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Enabling the copy-constant-to-alloca optimization in more instances

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Patch by Mohammad Fawaz

This patch allows lifetime calls to be ignored (and later erased) if we
know that the copy-constant-to-alloca optimization is going to happen.
The case that is missed is when the global variable is in a different address
space than the alloca (as shown in the example added to the lit test.)

This used to work before 6da31fa4a6

Differential Revision: https://reviews.llvm.org/D106573
This commit is contained in:
Andy Kaylor 2021-07-27 10:09:30 -07:00
parent cdd50ed2ff
commit fd18a762a0
2 changed files with 21 additions and 0 deletions
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2
lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
View File

@ -272,6 +272,8 @@ bool PointerReplacer::collectUsers(Instruction &I) {
return false;
} else if (isa<MemTransferInst>(Inst)) {
Worklist.insert(Inst);
} else if (Inst->isLifetimeStartOrEnd()) {
continue;
} else {
LLVM_DEBUG(dbgs() << "Cannot handle pointer user: " << *U << '\n');
return false;

19
test/Transforms/InstCombine/memcpy-from-global.ll
View File

@ -73,6 +73,7 @@ declare void @llvm.memcpy.p1i8.p1i8.i64(i8 addrspace(1)* nocapture, i8 addrspace
@G = constant %T {i8 1, [123 x i8] zeroinitializer }
@H = constant [2 x %U] zeroinitializer, align 16
@I = internal addrspace(1) constant [4 x float] zeroinitializer , align 4
define void @test2() {
; CHECK-LABEL: @test2(
@ -323,4 +324,22 @@ entry:
ret void
}
; Should replace alloca with global even when the global is in a different address space
define float @test11(i64 %i) {
; CHECK-LABEL: @test11(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[GEP:%.*]] = getelementptr [4 x float], [4 x float] addrspace(1)* @I, i64 0, i64 %i
; CHECK-NEXT: [[LD:%.*]] = load float, float addrspace(1)* [[GEP]]
; CHECK-NEXT: ret float [[LD]]
entry:
%a = alloca [4 x float], align 4
%b = bitcast [4 x float]* %a to i8*
call void @llvm.lifetime.start.p0i8(i64 16, i8* %b)
call void @llvm.memcpy.p0i8.p1i8.i64(i8* align 4 %b, i8 addrspace(1)* align 4 bitcast ([4 x float] addrspace(1)* @I to i8 addrspace(1)*), i64 16, i1 false)
%g = getelementptr inbounds [4 x float], [4 x float]* %a, i64 0, i64 %i
%r = load float, float* %g, align 4
ret float %r
}
attributes #0 = { null_pointer_is_valid }