fix instcombine merging GEPs through a PHI to only make the

result inbounds if all of the inputs are inbounds.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@125785 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/InstCombine/InstCombinePHI.cpp

@@ -118,6 +118,8 @@ Instruction *InstCombiner::FoldPHIArgGEPIntoPHI(PHINode &PN) {
   // especially bad when the PHIs are in the header of a loop.
   bool NeededPhi = false;
   
+  bool AllInBounds = true;
+  
   // Scan to see if all operands are the same opcode, and all have one use.
   for (unsigned i = 1; i != PN.getNumIncomingValues(); ++i) {
     GetElementPtrInst *GEP= dyn_cast<GetElementPtrInst>(PN.getIncomingValue(i));
@@ -125,6 +127,8 @@ Instruction *InstCombiner::FoldPHIArgGEPIntoPHI(PHINode &PN) {
       GEP->getNumOperands() != FirstInst->getNumOperands())
       return 0;
 
+    AllInBounds &= GEP->isInBounds();
+    
     // Keep track of whether or not all GEPs are of alloca pointers.
     if (AllBasePointersAreAllocas &&
         (!isa<AllocaInst>(GEP->getOperand(0)) ||
@@ -202,11 +206,11 @@ Instruction *InstCombiner::FoldPHIArgGEPIntoPHI(PHINode &PN) {
   }
   
   Value *Base = FixedOperands[0];
-  return cast<GEPOperator>(FirstInst)->isInBounds() ?
-    GetElementPtrInst::CreateInBounds(Base, FixedOperands.begin()+1,
-                                      FixedOperands.end()) :
+  GetElementPtrInst *NewGEP = 
     GetElementPtrInst::Create(Base, FixedOperands.begin()+1,
                               FixedOperands.end());
+  if (AllInBounds) NewGEP->setIsInbounds();
+  return NewGEP;
 }
 
 

test/Transforms/InstCombine/phi.ll

@@ -125,7 +125,7 @@ Exit:           ; preds = %Loop
 
 define i32* @test8({ i32, i32 } *%A, i1 %b) {
 BB0:
-        %X = getelementptr { i32, i32 } *%A, i32 0, i32 1
+        %X = getelementptr inbounds { i32, i32 } *%A, i32 0, i32 1
         br i1 %b, label %BB1, label %BB2
 
 BB1:
@@ -139,7 +139,7 @@ BB2:
 ; CHECK: @test8
 ; CHECK-NOT: phi
 ; CHECK: BB2:
-; CHECK-NEXT: %B = getelementptr 
+; CHECK-NEXT: %B = getelementptr %0 
 ; CHECK-NEXT: ret i32* %B
 }
 
@@ -525,3 +525,4 @@ Exit:           ; preds = %Loop
 ; CHECK: Exit:
 ; CHECK-NEXT: ret i32 %B
 }
+