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stage2 llvm: Elide more loads

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Adds optimizations for by-ref types to:
  - .struct_field_val
  - .slice_elem_val
  - .ptr_elem_val

I would have expected LLVM to be able to optimize away these
temporaries since we don't leak pointers to them and they are fed
straight from def to use, but empirically it does not.

Resolves https://github.com/ziglang/zig/issues/12713
Resolves https://github.com/ziglang/zig/issues/12638
This commit is contained in:
Cody Tapscott 2022-11-10 12:03:17 -07:00
parent 8f3880074f
commit a2f4de1663
1 changed files with 24 additions and 1 deletions
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23
src/codegen/llvm.zig
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@ -5644,6 +5644,14 @@ pub const FuncGen = struct {
const base_ptr = self.builder.buildExtractValue(slice, 0, "");
const indices: [1]*llvm.Value = .{index};
const ptr = self.builder.buildInBoundsGEP(llvm_elem_ty, base_ptr, &indices, indices.len, "");
if (isByRef(elem_ty)) {
if (self.canElideLoad(body_tail))
return ptr;
const target = self.dg.module.getTarget();
return self.loadByRef(ptr, elem_ty, elem_ty.abiAlignment(target), false);
}
return self.load(ptr, slice_ty);
}
@ -5709,6 +5717,14 @@ pub const FuncGen = struct {
const indices: [1]*llvm.Value = .{rhs};
break :ptr self.builder.buildInBoundsGEP(llvm_elem_ty, base_ptr, &indices, indices.len, "");
};
if (isByRef(elem_ty)) {
if (self.canElideLoad(body_tail))
return ptr;
const target = self.dg.module.getTarget();
return self.loadByRef(ptr, elem_ty, elem_ty.abiAlignment(target), false);
}
return self.load(ptr, ptr_ty);
}
@ -5832,7 +5848,14 @@ pub const FuncGen = struct {
const struct_llvm_ty = try self.dg.lowerType(struct_ty);
const field_ptr = self.builder.buildStructGEP(struct_llvm_ty, struct_llvm_val, llvm_field_index, "");
const field_ptr_ty = Type.initPayload(&ptr_ty_buf.base);
if (isByRef(field_ty)) {
if (canElideLoad(self, body_tail))
return field_ptr;
return self.loadByRef(field_ptr, field_ty, ptr_ty_buf.data.alignment(target), false);
} else {
return self.load(field_ptr, field_ptr_ty);
}
},
.Union => {
const union_llvm_ty = try self.dg.lowerType(struct_ty);