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fix cmpxchg with discarded result

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This commit is contained in:
Andrew Kelley 2019-08-02 14:47:26 -04:00
parent a5cb0f77d1
commit 90e64bc620
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GPG Key ID: 7C5F548F728501A9
2 changed files with 17 additions and 1 deletions
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8
src/codegen.cpp
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@ -4458,8 +4458,14 @@ static LLVMValueRef ir_render_cmpxchg(CodeGen *g, IrExecutable *executable, IrIn
return LLVMBuildSelect(g->builder, success_bit, LLVMConstNull(get_llvm_type(g, child_type)), payload_val, "");
}
// When the cmpxchg is discarded, the result location will have no bits.
if (!type_has_bits(instruction->result_loc->value.type)) {
return nullptr;
}
LLVMValueRef result_loc = ir_llvm_value(g, instruction->result_loc);
assert(type_has_bits(child_type));
src_assert(result_loc != nullptr, instruction->base.source_node);
src_assert(type_has_bits(child_type), instruction->base.source_node);
LLVMValueRef payload_val = LLVMBuildExtractValue(g->builder, result_val, 0, "");
LLVMValueRef val_ptr = LLVMBuildStructGEP(g->builder, result_loc, maybe_child_index, "");

10
test/stage1/behavior/atomics.zig
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@ -1,5 +1,6 @@
const std = @import("std");
const expect = std.testing.expect;
const expectEqual = std.testing.expectEqual;
const builtin = @import("builtin");
const AtomicRmwOp = builtin.AtomicRmwOp;
const AtomicOrder = builtin.AtomicOrder;
@ -90,3 +91,12 @@ test "cmpxchg with ptr" {
// expect(@cmpxchgStrong(u128, &x, 5678, 42, .SeqCst, .SeqCst) == null);
// expect(x == 42);
//}
test "cmpxchg with ignored result" {
var x: i32 = 1234;
var ptr = &x;
_ = @cmpxchgStrong(i32, &x, 1234, 5678, .Monotonic, .Monotonic);
expectEqual(i32(5678), x);
}