[InstCombine] Remove invariant group intrinsincs when comparing against null

We cannot leak any equivalency information by comparing against null
since null never has virtual metadata associated with it (when null is
not a valid dereferenceable pointer).

Instcombine seems to make sure that a null will be on the RHS, so we
don't have to check both operands.

This fixes a missed optimization in llvm-test-suite's MultiSource lambda
benchmark under -fstrict-vtable-pointers.

Reviewed By: Prazek

Differential Revision: https://reviews.llvm.org/D108734

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
index 7103761..0ff23b4 100644 (file)
--- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -5702,6 +5702,23 @@ static Instruction *foldICmpOfUAddOv(ICmpInst &I) {
   return ExtractValueInst::Create(UAddOv, 1);
 }
 
+static Instruction *foldICmpInvariantGroup(ICmpInst &I) {
+  if (!I.getOperand(0)->getType()->isPointerTy() ||
+      NullPointerIsDefined(
+          I.getParent()->getParent(),
+          I.getOperand(0)->getType()->getPointerAddressSpace())) {
+    return nullptr;
+  }
+  Instruction *Op;
+  if (match(I.getOperand(0), m_Instruction(Op)) &&
+      match(I.getOperand(1), m_Zero()) &&
+      Op->isLaunderOrStripInvariantGroup()) {
+    return ICmpInst::Create(Instruction::ICmp, I.getPredicate(),
+                            Op->getOperand(0), I.getOperand(1));
+  }
+  return nullptr;
+}
+
 Instruction *InstCombinerImpl::visitICmpInst(ICmpInst &I) {
   bool Changed = false;
   const SimplifyQuery Q = SQ.getWithInstruction(&I);
@@ -5942,6 +5959,9 @@ Instruction *InstCombinerImpl::visitICmpInst(ICmpInst &I) {
     if (Instruction *Res = foldVectorCmp(I, Builder))
       return Res;
 
+  if (Instruction *Res = foldICmpInvariantGroup(I))
+    return Res;
+
   return Changed ? &I : nullptr;
 }
 

diff --git a/llvm/test/Transforms/InstCombine/invariant.group.ll b/llvm/test/Transforms/InstCombine/invariant.group.ll
index a1ed714..da3d8a7 100644 (file)
--- a/llvm/test/Transforms/InstCombine/invariant.group.ll
+++ b/llvm/test/Transforms/InstCombine/invariant.group.ll
@@ -161,8 +161,7 @@ define i16 addrspace(42)* @skipWithDifferentTypesDifferentAddrspace(i8* %a) {
 
 define i1 @icmp_null_launder(i8* %a) {
 ; CHECK-LABEL: @icmp_null_launder(
-; CHECK-NEXT:    [[A2:%.*]] = call i8* @llvm.launder.invariant.group.p0i8(i8* [[A:%.*]])
-; CHECK-NEXT:    [[R:%.*]] = icmp eq i8* [[A2]], null
+; CHECK-NEXT:    [[R:%.*]] = icmp eq i8* [[A:%.*]], null
 ; CHECK-NEXT:    ret i1 [[R]]
 ;
   %a2 = call i8* @llvm.launder.invariant.group.p0i8(i8* %a)
@@ -172,8 +171,7 @@ define i1 @icmp_null_launder(i8* %a) {
 
 define i1 @icmp_null_strip(i8* %a) {
 ; CHECK-LABEL: @icmp_null_strip(
-; CHECK-NEXT:    [[A2:%.*]] = call i8* @llvm.strip.invariant.group.p0i8(i8* [[A:%.*]])
-; CHECK-NEXT:    [[R:%.*]] = icmp eq i8* [[A2]], null
+; CHECK-NEXT:    [[R:%.*]] = icmp eq i8* [[A:%.*]], null
 ; CHECK-NEXT:    ret i1 [[R]]
 ;
   %a2 = call i8* @llvm.strip.invariant.group.p0i8(i8* %a)
@@ -206,8 +204,7 @@ define i1 @icmp_null_strip_valid_null(i8* %a) #0 {
 ; Check that null always becomes the RHS
 define i1 @icmp_null_launder_lhs(i8* %a) {
 ; CHECK-LABEL: @icmp_null_launder_lhs(
-; CHECK-NEXT:    [[A2:%.*]] = call i8* @llvm.launder.invariant.group.p0i8(i8* [[A:%.*]])
-; CHECK-NEXT:    [[R:%.*]] = icmp eq i8* [[A2]], null
+; CHECK-NEXT:    [[R:%.*]] = icmp eq i8* [[A:%.*]], null
 ; CHECK-NEXT:    ret i1 [[R]]
 ;
   %a2 = call i8* @llvm.launder.invariant.group.p0i8(i8* %a)
@@ -217,9 +214,7 @@ define i1 @icmp_null_launder_lhs(i8* %a) {
 
 define i1 @icmp_null_launder_bitcasts(i32* %a) {
 ; CHECK-LABEL: @icmp_null_launder_bitcasts(
-; CHECK-NEXT:    [[A2:%.*]] = bitcast i32* [[A:%.*]] to i8*
-; CHECK-NEXT:    [[A3:%.*]] = call i8* @llvm.launder.invariant.group.p0i8(i8* [[A2]])
-; CHECK-NEXT:    [[R:%.*]] = icmp eq i8* [[A3]], null
+; CHECK-NEXT:    [[R:%.*]] = icmp eq i32* [[A:%.*]], null
 ; CHECK-NEXT:    ret i1 [[R]]
 ;
   %a2 = bitcast i32* %a to i8*