26049b8ce3
We can generalize the malloc-to-global transform for other allocation functions which are both a) removable, and b) have a known initialization value. One subtlety that I want to point out - mostly because I hadn't realized it was true until I took a closer look - is that the existing code doesn't prove that initialization/malloc happens only once. The initialization function can be called multiple times. This is correct without special handling for malloc as undef can map to any value previously written, but a non-undef initializing allocation it means we may end up memseting the new global repeatedly. In particular, this means it's not legal to fold the memset into the initializer of the global. Differential Revision: https://reviews.llvm.org/D117503
50 lines
1.6 KiB
LLVM
50 lines
1.6 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
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; RUN: opt -passes=globalopt -S < %s | FileCheck %s
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@g = internal global i32* null, align 8
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define signext i32 @f() local_unnamed_addr {
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; CHECK-LABEL: @f(
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; CHECK-NEXT: entry:
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; CHECK-NEXT: call void @llvm.memset.p0i8.i64(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @g.body, i32 0, i32 0), i8 0, i64 4, i1 false)
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; CHECK-NEXT: store i16 -1, i16* bitcast ([4 x i8]* @g.body to i16*), align 2
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; CHECK-NEXT: ret i32 0
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;
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entry:
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%call = call i8* @calloc(i64 1, i64 4)
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%b = bitcast i8* %call to i32*
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store i32* %b, i32** @g, align 8
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%b2 = bitcast i8* %call to i16*
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store i16 -1, i16* %b2
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ret i32 0
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}
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define signext i32 @main() {
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; CHECK-LABEL: @main(
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; CHECK-NEXT: entry:
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; CHECK-NEXT: [[CALL:%.*]] = call signext i32 @f()
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; CHECK-NEXT: call void @f1()
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; CHECK-NEXT: store i32 1, i32* bitcast ([4 x i8]* @g.body to i32*), align 4
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; CHECK-NEXT: call void @f1()
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; CHECK-NEXT: store i8 2, i8* getelementptr inbounds ([4 x i8], [4 x i8]* @g.body, i32 0, i32 0), align 4
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; CHECK-NEXT: call void @f1()
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; CHECK-NEXT: [[RES:%.*]] = load i32, i32* bitcast ([4 x i8]* @g.body to i32*), align 4
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; CHECK-NEXT: ret i32 [[RES]]
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;
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entry:
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%call = call signext i32 @f()
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call void @f1()
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%v0 = load i32*, i32** @g, align 8
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store i32 1, i32* %v0, align 4
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call void @f1()
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%v1 = load i8*, i8** bitcast (i32** @g to i8**), align 8
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store i8 2, i8* %v1, align 4
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call void @f1()
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%v2 = load i32*, i32** @g, align 8
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%res = load i32, i32* %v2, align 4
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ret i32 %res
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}
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declare noalias align 16 i8* @calloc(i64, i64)
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declare void @f1()
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