[llvm] 929cbe7 - [InstCombine] Intersect nowrap flags between geps while folding into phi
Antonio Frighetto via llvm-commits
llvm-commits at lists.llvm.org
Wed Nov 13 10:46:09 PST 2024
Author: Antonio Frighetto
Date: 2024-11-13T19:42:06+01:00
New Revision: 929cbe7f596733f85cd274485acc19442dd34a80
URL: https://github.com/llvm/llvm-project/commit/929cbe7f596733f85cd274485acc19442dd34a80
DIFF: https://github.com/llvm/llvm-project/commit/929cbe7f596733f85cd274485acc19442dd34a80.diff
LOG: [InstCombine] Intersect nowrap flags between geps while folding into phi
A miscompilation issue has been addressed with refined checking.
Fixes: https://github.com/llvm/llvm-project/issues/115149.
Added:
Modified:
llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp
llvm/test/Transforms/InstCombine/opaque-ptr.ll
llvm/test/Transforms/InstCombine/phi.ll
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp b/llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp
index cb5c4473051262..1fcf1c570addac 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp
@@ -545,7 +545,8 @@ Instruction *InstCombinerImpl::foldPHIArgGEPIntoPHI(PHINode &PN) {
// especially bad when the PHIs are in the header of a loop.
bool NeededPhi = false;
- GEPNoWrapFlags NW = GEPNoWrapFlags::all();
+ // Remember flags of the first phi-operand getelementptr.
+ GEPNoWrapFlags NW = FirstInst->getNoWrapFlags();
// Scan to see if all operands are the same opcode, and all have one user.
for (Value *V : drop_begin(PN.incoming_values())) {
diff --git a/llvm/test/Transforms/InstCombine/opaque-ptr.ll b/llvm/test/Transforms/InstCombine/opaque-ptr.ll
index a52a07389baee2..4e0355e61739a8 100644
--- a/llvm/test/Transforms/InstCombine/opaque-ptr.ll
+++ b/llvm/test/Transforms/InstCombine/opaque-ptr.ll
@@ -549,7 +549,7 @@ define ptr @phi_of_gep_flags_1(i1 %c, ptr %p) {
; CHECK: else:
; CHECK-NEXT: br label [[JOIN]]
; CHECK: join:
-; CHECK-NEXT: [[PHI:%.*]] = getelementptr nusw nuw i8, ptr [[P:%.*]], i64 4
+; CHECK-NEXT: [[PHI:%.*]] = getelementptr nusw i8, ptr [[P:%.*]], i64 4
; CHECK-NEXT: ret ptr [[PHI]]
;
br i1 %c, label %if, label %else
diff --git a/llvm/test/Transforms/InstCombine/phi.ll b/llvm/test/Transforms/InstCombine/phi.ll
index c726947318eb40..c3548590d7f57a 100644
--- a/llvm/test/Transforms/InstCombine/phi.ll
+++ b/llvm/test/Transforms/InstCombine/phi.ll
@@ -2795,14 +2795,13 @@ BB5: ; preds = %BB4
ret void
}
-; FIXME: This is a miscompilation.
define i64 @wrong_gep_arg_into_phi(ptr noundef %ptr) {
; CHECK-LABEL: @wrong_gep_arg_into_phi(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[FOR_COND:%.*]]
; CHECK: for.cond:
; CHECK-NEXT: [[PTR_PN:%.*]] = phi ptr [ [[PTR:%.*]], [[ENTRY:%.*]] ], [ [[DOTPN:%.*]], [[FOR_COND]] ]
-; CHECK-NEXT: [[DOTPN]] = getelementptr inbounds nuw i8, ptr [[PTR_PN]], i64 1
+; CHECK-NEXT: [[DOTPN]] = getelementptr i8, ptr [[PTR_PN]], i64 1
; CHECK-NEXT: [[VAL:%.*]] = load i8, ptr [[DOTPN]], align 1
; CHECK-NEXT: [[COND_NOT:%.*]] = icmp eq i8 [[VAL]], 0
; CHECK-NEXT: br i1 [[COND_NOT]], label [[EXIT:%.*]], label [[FOR_COND]]
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