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compiler_rt: implement __mulxf3 for f80
This commit is contained in:
Cody Tapscott
parent
5195b87639
commit
d760cae2b1
@ -226,23 +226,26 @@ comptime {
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@export(__addsf3, .{ .name = "__addsf3", .linkage = linkage });
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const __adddf3 = @import("compiler_rt/addXf3.zig").__adddf3;
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@export(__adddf3, .{ .name = "__adddf3", .linkage = linkage });
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const __addtf3 = @import("compiler_rt/addXf3.zig").__addtf3;
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@export(__addtf3, .{ .name = "__addtf3", .linkage = linkage });
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const __addxf3 = @import("compiler_rt/addXf3.zig").__addxf3;
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@export(__addxf3, .{ .name = "__addxf3", .linkage = linkage });
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const __addtf3 = @import("compiler_rt/addXf3.zig").__addtf3;
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@export(__addtf3, .{ .name = "__addtf3", .linkage = linkage });
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const __subsf3 = @import("compiler_rt/addXf3.zig").__subsf3;
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@export(__subsf3, .{ .name = "__subsf3", .linkage = linkage });
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const __subdf3 = @import("compiler_rt/addXf3.zig").__subdf3;
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@export(__subdf3, .{ .name = "__subdf3", .linkage = linkage });
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const __subtf3 = @import("compiler_rt/addXf3.zig").__subtf3;
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@export(__subtf3, .{ .name = "__subtf3", .linkage = linkage });
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const __subxf3 = @import("compiler_rt/addXf3.zig").__subxf3;
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@export(__subxf3, .{ .name = "__subxf3", .linkage = linkage });
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const __subtf3 = @import("compiler_rt/addXf3.zig").__subtf3;
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@export(__subtf3, .{ .name = "__subtf3", .linkage = linkage });
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const __mulsf3 = @import("compiler_rt/mulXf3.zig").__mulsf3;
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@export(__mulsf3, .{ .name = "__mulsf3", .linkage = linkage });
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const __muldf3 = @import("compiler_rt/mulXf3.zig").__muldf3;
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@export(__muldf3, .{ .name = "__muldf3", .linkage = linkage });
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const __mulxf3 = @import("compiler_rt/mulXf3.zig").__mulxf3;
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@export(__mulxf3, .{ .name = "__mulxf3", .linkage = linkage });
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const __multf3 = @import("compiler_rt/mulXf3.zig").__multf3;
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@export(__multf3, .{ .name = "__multf3", .linkage = linkage });
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@ -3,12 +3,16 @@
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// https://github.com/llvm/llvm-project/blob/2ffb1b0413efa9a24eb3c49e710e36f92e2cb50b/compiler-rt/lib/builtins/fp_mul_impl.inc
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const std = @import("std");
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const math = std.math;
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const builtin = @import("builtin");
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const compiler_rt = @import("../compiler_rt.zig");
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pub fn __multf3(a: f128, b: f128) callconv(.C) f128 {
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return mulXf3(f128, a, b);
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}
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pub fn __mulxf3(a: f80, b: f80) callconv(.C) f80 {
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return mulXf3(f80, a, b);
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}
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pub fn __muldf3(a: f64, b: f64) callconv(.C) f64 {
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return mulXf3(f64, a, b);
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}
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@ -29,30 +33,36 @@ pub fn __aeabi_dmul(a: f64, b: f64) callconv(.C) f64 {
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fn mulXf3(comptime T: type, a: T, b: T) T {
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@setRuntimeSafety(builtin.is_test);
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const typeWidth = @typeInfo(T).Float.bits;
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const significandBits = math.floatMantissaBits(T);
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const fractionalBits = math.floatFractionalBits(T);
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const exponentBits = math.floatExponentBits(T);
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const Z = std.meta.Int(.unsigned, typeWidth);
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const significandBits = std.math.floatMantissaBits(T);
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const exponentBits = std.math.floatExponentBits(T);
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// ZSignificand is large enough to contain the significand, including an explicit integer bit
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const ZSignificand = PowerOfTwoSignificandZ(T);
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const ZSignificandBits = @typeInfo(ZSignificand).Int.bits;
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const roundBit = (1 << (ZSignificandBits - 1));
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const signBit = (@as(Z, 1) << (significandBits + exponentBits));
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const maxExponent = ((1 << exponentBits) - 1);
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const exponentBias = (maxExponent >> 1);
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const implicitBit = (@as(Z, 1) << significandBits);
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const quietBit = implicitBit >> 1;
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const significandMask = implicitBit - 1;
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const integerBit = (@as(ZSignificand, 1) << fractionalBits);
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const quietBit = integerBit >> 1;
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const significandMask = (@as(Z, 1) << significandBits) - 1;
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const absMask = signBit - 1;
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const exponentMask = absMask ^ significandMask;
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const qnanRep = exponentMask | quietBit;
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const infRep = @bitCast(Z, std.math.inf(T));
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const qnanRep = @bitCast(Z, math.nan(T)) | quietBit;
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const infRep = @bitCast(Z, math.inf(T));
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const minNormalRep = @bitCast(Z, math.floatMin(T));
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const aExponent = @truncate(u32, (@bitCast(Z, a) >> significandBits) & maxExponent);
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const bExponent = @truncate(u32, (@bitCast(Z, b) >> significandBits) & maxExponent);
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const productSign: Z = (@bitCast(Z, a) ^ @bitCast(Z, b)) & signBit;
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var aSignificand: Z = @bitCast(Z, a) & significandMask;
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var bSignificand: Z = @bitCast(Z, b) & significandMask;
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var aSignificand: ZSignificand = @intCast(ZSignificand, @bitCast(Z, a) & significandMask);
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var bSignificand: ZSignificand = @intCast(ZSignificand, @bitCast(Z, b) & significandMask);
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var scale: i32 = 0;
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// Detect if a or b is zero, denormal, infinity, or NaN.
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@ -93,38 +103,40 @@ fn mulXf3(comptime T: type, a: T, b: T) T {
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// one or both of a or b is denormal, the other (if applicable) is a
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// normal number. Renormalize one or both of a and b, and set scale to
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// include the necessary exponent adjustment.
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if (aAbs < implicitBit) scale += normalize(T, &aSignificand);
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if (bAbs < implicitBit) scale += normalize(T, &bSignificand);
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if (aAbs < minNormalRep) scale += normalize(T, &aSignificand);
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if (bAbs < minNormalRep) scale += normalize(T, &bSignificand);
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}
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// Or in the implicit significand bit. (If we fell through from the
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// denormal path it was already set by normalize( ), but setting it twice
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// won't hurt anything.)
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aSignificand |= implicitBit;
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bSignificand |= implicitBit;
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aSignificand |= integerBit;
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bSignificand |= integerBit;
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// Get the significand of a*b. Before multiplying the significands, shift
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// one of them left to left-align it in the field. Thus, the product will
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// have (exponentBits + 2) integral digits, all but two of which must be
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// zero. Normalizing this result is just a conditional left-shift by one
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// and bumping the exponent accordingly.
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var productHi: Z = undefined;
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var productLo: Z = undefined;
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wideMultiply(Z, aSignificand, bSignificand << exponentBits, &productHi, &productLo);
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var productHi: ZSignificand = undefined;
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var productLo: ZSignificand = undefined;
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const left_align_shift = ZSignificandBits - fractionalBits - 1;
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wideMultiply(ZSignificand, aSignificand, bSignificand << left_align_shift, &productHi, &productLo);
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var productExponent: i32 = @bitCast(i32, aExponent +% bExponent) -% exponentBias +% scale;
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var productExponent: i32 = @intCast(i32, aExponent + bExponent) - exponentBias + scale;
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// Normalize the significand, adjust exponent if needed.
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if ((productHi & implicitBit) != 0) {
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if ((productHi & integerBit) != 0) {
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productExponent +%= 1;
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} else {
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productHi = (productHi << 1) | (productLo >> (typeWidth - 1));
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productHi = (productHi << 1) | (productLo >> (ZSignificandBits - 1));
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productLo = productLo << 1;
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}
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// If we have overflowed the type, return +/- infinity.
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if (productExponent >= maxExponent) return @bitCast(T, infRep | productSign);
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var result: Z = undefined;
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if (productExponent <= 0) {
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// Result is denormal before rounding
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//
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@ -133,35 +145,49 @@ fn mulXf3(comptime T: type, a: T, b: T) T {
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// handle this case separately, but we make it a special case to
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// simplify the shift logic.
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const shift: u32 = @truncate(u32, @as(Z, 1) -% @bitCast(u32, productExponent));
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if (shift >= typeWidth) return @bitCast(T, productSign);
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if (shift >= ZSignificandBits) return @bitCast(T, productSign);
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// Otherwise, shift the significand of the result so that the round
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// bit is the high bit of productLo.
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wideRightShiftWithSticky(Z, &productHi, &productLo, shift);
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const sticky = wideShrWithTruncation(ZSignificand, &productHi, &productLo, shift);
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productLo |= @boolToInt(sticky);
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result = productHi;
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} else {
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// Result is normal before rounding; insert the exponent.
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productHi &= significandMask;
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productHi |= @as(Z, @bitCast(u32, productExponent)) << significandBits;
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result = productHi & significandMask;
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result |= @intCast(Z, productExponent) << significandBits;
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}
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// Insert the sign of the result:
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productHi |= productSign;
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// Final rounding. The final result may overflow to infinity, or underflow
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// to zero, but those are the correct results in those cases. We use the
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// default IEEE-754 round-to-nearest, ties-to-even rounding mode.
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if (productLo > signBit) productHi +%= 1;
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if (productLo == signBit) productHi +%= productHi & 1;
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return @bitCast(T, productHi);
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if (productLo > roundBit) result +%= 1;
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if (productLo == roundBit) result +%= result & 1;
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// Restore any explicit integer bit, if it was rounded off
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if (significandBits != fractionalBits) {
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if ((result >> significandBits) != 0) result |= integerBit;
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}
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// Insert the sign of the result:
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result |= productSign;
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return @bitCast(T, result);
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}
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fn wideMultiply(comptime Z: type, a: Z, b: Z, hi: *Z, lo: *Z) void {
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@setRuntimeSafety(builtin.is_test);
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switch (Z) {
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u16 => {
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// 16x16 --> 32 bit multiply
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const product = @as(u32, a) * @as(u32, b);
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hi.* = @intCast(u16, product >> 16);
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lo.* = @truncate(u16, product);
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},
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u32 => {
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// 32x32 --> 64 bit multiply
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const product = @as(u64, a) * @as(u64, b);
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hi.* = @truncate(u32, product >> 32);
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hi.* = @intCast(u32, product >> 32);
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lo.* = @truncate(u32, product);
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},
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u64 => {
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@ -170,7 +196,7 @@ fn wideMultiply(comptime Z: type, a: Z, b: Z, hi: *Z, lo: *Z) void {
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return @truncate(u32, x);
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}
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fn hiWord(x: u64) u64 {
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return @truncate(u32, x >> 32);
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return @intCast(u32, x >> 32);
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}
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};
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// 64x64 -> 128 wide multiply for platforms that don't have such an operation;
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@ -264,34 +290,45 @@ fn wideMultiply(comptime Z: type, a: Z, b: Z, hi: *Z, lo: *Z) void {
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}
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}
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fn normalize(comptime T: type, significand: *std.meta.Int(.unsigned, @typeInfo(T).Float.bits)) i32 {
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@setRuntimeSafety(builtin.is_test);
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const Z = std.meta.Int(.unsigned, @typeInfo(T).Float.bits);
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const significandBits = std.math.floatMantissaBits(T);
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const implicitBit = @as(Z, 1) << significandBits;
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/// Returns a power-of-two integer type that is large enough to contain
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/// the significand of T, including an explicit integer bit
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fn PowerOfTwoSignificandZ(comptime T: type) type {
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const bits = math.ceilPowerOfTwoAssert(u16, math.floatFractionalBits(T) + 1);
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return std.meta.Int(.unsigned, bits);
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}
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const shift = @clz(Z, significand.*) - @clz(Z, implicitBit);
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significand.* <<= @intCast(std.math.Log2Int(Z), shift);
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fn normalize(comptime T: type, significand: *PowerOfTwoSignificandZ(T)) i32 {
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@setRuntimeSafety(builtin.is_test);
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const Z = PowerOfTwoSignificandZ(T);
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const integerBit = @as(Z, 1) << math.floatFractionalBits(T);
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const shift = @clz(Z, significand.*) - @clz(Z, integerBit);
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significand.* <<= @intCast(math.Log2Int(Z), shift);
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return @as(i32, 1) - shift;
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}
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fn wideRightShiftWithSticky(comptime Z: type, hi: *Z, lo: *Z, count: u32) void {
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// Returns `true` if the right shift is inexact (i.e. any bit shifted out is non-zero)
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//
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// This is analogous to an shr version of `@shlWithOverflow`
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fn wideShrWithTruncation(comptime Z: type, hi: *Z, lo: *Z, count: u32) bool {
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@setRuntimeSafety(builtin.is_test);
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const typeWidth = @typeInfo(Z).Int.bits;
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const S = std.math.Log2Int(Z);
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const S = math.Log2Int(Z);
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var inexact = false;
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if (count < typeWidth) {
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const sticky = @boolToInt((lo.* << @intCast(S, typeWidth -% count)) != 0);
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lo.* = (hi.* << @intCast(S, typeWidth -% count)) | (lo.* >> @intCast(S, count)) | sticky;
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inexact = (lo.* << @intCast(S, typeWidth -% count)) != 0;
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lo.* = (hi.* << @intCast(S, typeWidth -% count)) | (lo.* >> @intCast(S, count));
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hi.* = hi.* >> @intCast(S, count);
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} else if (count < 2 * typeWidth) {
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const sticky = @boolToInt((hi.* << @intCast(S, 2 * typeWidth -% count) | lo.*) != 0);
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lo.* = hi.* >> @intCast(S, count -% typeWidth) | sticky;
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inexact = (hi.* << @intCast(S, 2 * typeWidth -% count) | lo.*) != 0;
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lo.* = hi.* >> @intCast(S, count -% typeWidth);
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hi.* = 0;
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} else {
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const sticky = @boolToInt((hi.* | lo.*) != 0);
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lo.* = sticky;
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inexact = (hi.* | lo.*) != 0;
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lo.* = 0;
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hi.* = 0;
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}
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return inexact;
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}
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test {
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@ -2,10 +2,15 @@
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//
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// https://github.com/llvm/llvm-project/blob/2ffb1b0413efa9a24eb3c49e710e36f92e2cb50b/compiler-rt/test/builtins/Unit/multf3_test.c
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const std = @import("std");
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const math = std.math;
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const qnan128 = @bitCast(f128, @as(u128, 0x7fff800000000000) << 64);
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const inf128 = @bitCast(f128, @as(u128, 0x7fff000000000000) << 64);
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const __multf3 = @import("mulXf3.zig").__multf3;
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const __mulxf3 = @import("mulXf3.zig").__mulxf3;
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const __muldf3 = @import("mulXf3.zig").__muldf3;
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const __mulsf3 = @import("mulXf3.zig").__mulsf3;
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// return true if equal
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// use two 64-bit integers intead of one 128-bit integer
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@ -97,4 +102,66 @@ test "multf3" {
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0x3f90000000000000,
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0x0,
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);
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try test__multf3(0x1.0000_0000_0000_0000_0000_0000_0001p+0, 0x1.8p+5, 0x4004_8000_0000_0000, 0x0000_0000_0000_0002);
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try test__multf3(0x1.0000_0000_0000_0000_0000_0000_0002p+0, 0x1.8p+5, 0x4004_8000_0000_0000, 0x0000_0000_0000_0003);
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}
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const qnan80 = @bitCast(f80, @bitCast(u80, math.nan(f80)) | (1 << (math.floatFractionalBits(f80) - 1)));
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fn test__mulxf3(a: f80, b: f80, expected: u80) !void {
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const x = __mulxf3(a, b);
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const rep = @bitCast(u80, x);
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if (rep == expected)
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return;
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if (math.isNan(@bitCast(f80, expected)) and math.isNan(x))
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return; // We don't currently test NaN payload propagation
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return error.TestFailed;
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}
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test "mulxf3" {
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// NaN * any = NaN
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try test__mulxf3(qnan80, 0x1.23456789abcdefp+5, @bitCast(u80, qnan80));
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try test__mulxf3(@bitCast(f80, @as(u80, 0x7fff_8000_8000_3000_0000)), 0x1.23456789abcdefp+5, @bitCast(u80, qnan80));
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// any * NaN = NaN
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try test__mulxf3(0x1.23456789abcdefp+5, qnan80, @bitCast(u80, qnan80));
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try test__mulxf3(0x1.23456789abcdefp+5, @bitCast(f80, @as(u80, 0x7fff_8000_8000_3000_0000)), @bitCast(u80, qnan80));
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// NaN * inf = NaN
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try test__mulxf3(qnan80, math.inf(f80), @bitCast(u80, qnan80));
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// inf * NaN = NaN
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try test__mulxf3(math.inf(f80), qnan80, @bitCast(u80, qnan80));
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// inf * inf = inf
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try test__mulxf3(math.inf(f80), math.inf(f80), @bitCast(u80, math.inf(f80)));
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// inf * -inf = -inf
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try test__mulxf3(math.inf(f80), -math.inf(f80), @bitCast(u80, -math.inf(f80)));
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// -inf + inf = -inf
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try test__mulxf3(-math.inf(f80), math.inf(f80), @bitCast(u80, -math.inf(f80)));
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// inf * any = inf
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try test__mulxf3(math.inf(f80), 0x1.2335653452436234723489432abcdefp+5, @bitCast(u80, math.inf(f80)));
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// any * inf = inf
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try test__mulxf3(0x1.2335653452436234723489432abcdefp+5, math.inf(f80), @bitCast(u80, math.inf(f80)));
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// any * any
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try test__mulxf3(0x1.0p+0, 0x1.dcba987654321p+5, 0x4004_ee5d_4c3b_2a19_0800);
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try test__mulxf3(0x1.0000_0000_0000_0004p+0, 0x1.8p+5, 0x4004_C000_0000_0000_0003); // exact
|
||||
|
||||
try test__mulxf3(0x1.0000_0000_0000_0002p+0, 0x1.0p+5, 0x4004_8000_0000_0000_0001); // exact
|
||||
try test__mulxf3(0x1.0000_0000_0000_0002p+0, 0x1.7ffep+5, 0x4004_BFFF_0000_0000_0001); // round down
|
||||
try test__mulxf3(0x1.0000_0000_0000_0002p+0, 0x1.8p+5, 0x4004_C000_0000_0000_0002); // round up to even
|
||||
try test__mulxf3(0x1.0000_0000_0000_0002p+0, 0x1.8002p+5, 0x4004_C001_0000_0000_0002); // round up
|
||||
try test__mulxf3(0x1.0000_0000_0000_0002p+0, 0x1.0p+6, 0x4005_8000_0000_0000_0001); // exact
|
||||
|
||||
try test__mulxf3(0x1.0000_0001p+0, 0x1.0000_0001p+0, 0x3FFF_8000_0001_0000_0000); // round down to even
|
||||
try test__mulxf3(0x1.0000_0001p+0, 0x1.0000_0001_0002p+0, 0x3FFF_8000_0001_0001_0001); // round up
|
||||
}
|
||||
|
||||
Loading…
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Reference in New Issue
Block a user