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[GVN] Remove users from ICF when RAUWing loads

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When performing store to load forwarding, replacing users of the
load may turn an indirect call into one with a known callee, in
which case it might become willreturn, invalidating cached ICF
information. Avoid this by removing users.

This is a bit more aggressive than strictly necessary (e.g. this
shouldn't be necessary when doing load-load CSE), but better safe
than sorry.

Fixes https://github.com/llvm/llvm-project/issues/48805.
This commit is contained in:
Nikita Popov 2023-10-05 11:19:26 +02:00
parent 59e75b7df2
commit 46aac949bc
2 changed files with 52 additions and 0 deletions
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3
llvm/lib/Transforms/Scalar/GVN.cpp
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@ -1472,6 +1472,7 @@ void GVNPass::eliminatePartiallyRedundantLoad(
// Perform PHI construction.
Value *V = ConstructSSAForLoadSet(Load, ValuesPerBlock, *this);
// ConstructSSAForLoadSet is responsible for combining metadata.
ICF->replaceUsersOf(Load);
Load->replaceAllUsesWith(V);
if (isa<PHINode>(V))
V->takeName(Load);
@ -1891,6 +1892,7 @@ bool GVNPass::processNonLocalLoad(LoadInst *Load) {
// Perform PHI construction.
Value *V = ConstructSSAForLoadSet(Load, ValuesPerBlock, *this);
// ConstructSSAForLoadSet is responsible for combining metadata.
ICF->removeUsersOf(Load);
Load->replaceAllUsesWith(V);
if (isa<PHINode>(V))
@ -2165,6 +2167,7 @@ bool GVNPass::processLoad(LoadInst *L) {
Value *AvailableValue = AV->MaterializeAdjustedValue(L, L, *this);
// MaterializeAdjustedValue is responsible for combining metadata.
ICF->removeUsersOf(L);
L->replaceAllUsesWith(AvailableValue);
markInstructionForDeletion(L);
if (MSSAU)

49
llvm/test/Transforms/GVN/pr48805.ll Normal file
View File

@ -0,0 +1,49 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 3
; RUN: opt -S -passes=gvn < %s | FileCheck %s
declare void @willreturn() nounwind willreturn
declare void @capture(ptr)
; Make sure ICF is invalidated when the callee becomes known.
define i64 @test(ptr %p) {
; CHECK-LABEL: define i64 @test(
; CHECK-SAME: ptr [[P:%.*]]) {
; CHECK-NEXT: entry:
; CHECK-NEXT: [[A:%.*]] = alloca [2 x ptr], align 8
; CHECK-NEXT: [[A2:%.*]] = getelementptr ptr, ptr [[A]], i64 1
; CHECK-NEXT: call void @capture(ptr [[A]])
; CHECK-NEXT: br i1 false, label [[IF:%.*]], label [[ENTRY_EXIT_CRIT_EDGE:%.*]]
; CHECK: entry.exit_crit_edge:
; CHECK-NEXT: [[RES_PRE:%.*]] = load i64, ptr [[A2]], align 8
; CHECK-NEXT: br label [[EXIT:%.*]]
; CHECK: if:
; CHECK-NEXT: [[P1:%.*]] = load ptr, ptr [[A2]], align 8
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
; CHECK-NEXT: [[RES:%.*]] = phi i64 [ [[RES_PRE]], [[ENTRY_EXIT_CRIT_EDGE]] ], [ undef, [[IF]] ]
; CHECK-NEXT: store ptr @willreturn, ptr [[P]], align 8
; CHECK-NEXT: tail call void @willreturn()
; CHECK-NEXT: ret i64 [[RES]]
;
entry:
%a = alloca [2 x ptr], align 8
%a2 = getelementptr ptr, ptr %a, i64 1
call void @capture(ptr %a)
br i1 false, label %if, label %exit
if:
%p0 = load ptr, ptr %a, align 8
%p1 = load ptr, ptr %a2, align 8
br label %exit
exit:
store ptr @willreturn, ptr %p
%p2 = load ptr, ptr %a, align 8
%pgocount.i = load i64, ptr %p2, align 8
%fn = load ptr, ptr %p
tail call void %fn()
%res = load i64, ptr %a2, align 8
ret i64 %res
}