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stage1/stage2: Simplify divTrunc impl

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According to the documentation, `divTrunc` is "Truncated division.
Rounds toward zero". Lower it as a straightforward fdiv + trunc sequence
to make it behave as expected with mixed positive/negative operands.

Closes #10001
This commit is contained in:
LemonBoy 2021-10-24 17:11:43 +02:00
parent 94879506ea
commit 811766e1cf
3 changed files with 14 additions and 33 deletions
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11
src/codegen/llvm.zig
View File

@ -2874,13 +2874,8 @@ pub const FuncGen = struct {
const inst_ty = self.air.typeOfIndex(inst);
if (inst_ty.isRuntimeFloat()) {
const result_llvm_ty = try self.dg.llvmType(inst_ty);
const zero = result_llvm_ty.constNull();
const result = self.builder.buildFDiv(lhs, rhs, "");
const ceiled = try self.callCeil(result, inst_ty);
const floored = try self.callFloor(result, inst_ty);
const ltz = self.builder.buildFCmp(.OLT, lhs, zero, "");
return self.builder.buildSelect(ltz, ceiled, floored, "");
return self.callTrunc(result, inst_ty);
}
if (inst_ty.isSignedInt()) return self.builder.buildSDiv(lhs, rhs, "");
return self.builder.buildUDiv(lhs, rhs, "");
@ -3641,6 +3636,10 @@ pub const FuncGen = struct {
return self.callFloatUnary(arg, ty, "ceil");
}
fn callTrunc(self: *FuncGen, arg: *const llvm.Value, ty: Type) !*const llvm.Value {
return self.callFloatUnary(arg, ty, "trunc");
}
fn callFloatUnary(self: *FuncGen, arg: *const llvm.Value, ty: Type, name: []const u8) !*const llvm.Value {
const target = self.dg.module.getTarget();

28
src/stage1/codegen.cpp
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@ -2964,33 +2964,7 @@ static LLVMValueRef gen_div(CodeGen *g, bool want_runtime_safety, bool want_fast
}
return result;
case DivKindTrunc:
{
LLVMBasicBlockRef ltz_block = LLVMAppendBasicBlock(g->cur_fn_val, "DivTruncLTZero");
LLVMBasicBlockRef gez_block = LLVMAppendBasicBlock(g->cur_fn_val, "DivTruncGEZero");
LLVMBasicBlockRef end_block = LLVMAppendBasicBlock(g->cur_fn_val, "DivTruncEnd");
LLVMValueRef ltz = LLVMBuildFCmp(g->builder, LLVMRealOLT, val1, zero, "");
if (operand_type->id == ZigTypeIdVector) {
ltz = ZigLLVMBuildOrReduce(g->builder, ltz);
}
LLVMBuildCondBr(g->builder, ltz, ltz_block, gez_block);
LLVMPositionBuilderAtEnd(g->builder, ltz_block);
LLVMValueRef ceiled = gen_float_op(g, result, operand_type, BuiltinFnIdCeil);
LLVMBasicBlockRef ceiled_end_block = LLVMGetInsertBlock(g->builder);
LLVMBuildBr(g->builder, end_block);
LLVMPositionBuilderAtEnd(g->builder, gez_block);
LLVMValueRef floored = gen_float_op(g, result, operand_type, BuiltinFnIdFloor);
LLVMBasicBlockRef floored_end_block = LLVMGetInsertBlock(g->builder);
LLVMBuildBr(g->builder, end_block);
LLVMPositionBuilderAtEnd(g->builder, end_block);
LLVMValueRef phi = LLVMBuildPhi(g->builder, get_llvm_type(g, operand_type), "");
LLVMValueRef incoming_values[] = { ceiled, floored };
LLVMBasicBlockRef incoming_blocks[] = { ceiled_end_block, floored_end_block };
LLVMAddIncoming(phi, incoming_values, incoming_blocks, 2);
return phi;
}
return gen_float_op(g, result, operand_type, BuiltinFnIdTrunc);
case DivKindFloor:
return gen_float_op(g, result, operand_type, BuiltinFnIdFloor);
}

8
test/behavior/math.zig
View File

@ -282,12 +282,20 @@ fn testDivision() !void {
try expect(divTrunc(i32, 5, 3) == 1);
try expect(divTrunc(i32, -5, 3) == -1);
try expect(divTrunc(i32, 9, -10) == 0);
try expect(divTrunc(i32, -9, 10) == 0);
try expect(divTrunc(f16, 5.0, 3.0) == 1.0);
try expect(divTrunc(f16, -5.0, 3.0) == -1.0);
try expect(divTrunc(f16, 9.0, -10.0) == 0.0);
try expect(divTrunc(f16, -9.0, 10.0) == 0.0);
try expect(divTrunc(f32, 5.0, 3.0) == 1.0);
try expect(divTrunc(f32, -5.0, 3.0) == -1.0);
try expect(divTrunc(f32, 9.0, -10.0) == 0.0);
try expect(divTrunc(f32, -9.0, 10.0) == 0.0);
try expect(divTrunc(f64, 5.0, 3.0) == 1.0);
try expect(divTrunc(f64, -5.0, 3.0) == -1.0);
try expect(divTrunc(f64, 9.0, -10.0) == 0.0);
try expect(divTrunc(f64, -9.0, 10.0) == 0.0);
try expect(divTrunc(i32, 10, 12) == 0);
try expect(divTrunc(i32, -14, 12) == -1);
try expect(divTrunc(i32, -2, 12) == 0);