teach phi translation of GEPs to simplify geps like 'gep x, 0'.
This allows us to compile the example from PR5313 into:
LBB1_2: ## %bb
incl %ecx
movb %al, (%rsi)
movslq %ecx, %rax
movb (%rdi,%rax), %al
testb %al, %al
jne LBB1_2
instead of:
LBB1_2: ## %bb
movslq %eax, %rcx
incl %eax
movb (%rdi,%rcx), %cl
movb %cl, (%rsi)
movslq %eax, %rcx
cmpb $0, (%rdi,%rcx)
jne LBB1_2
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@89981 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/MemoryDependenceAnalysis.cpp b/lib/Analysis/MemoryDependenceAnalysis.cpp
index 6bffca6..d749751 100644
--- a/lib/Analysis/MemoryDependenceAnalysis.cpp
+++ b/lib/Analysis/MemoryDependenceAnalysis.cpp
@@ -20,6 +20,7 @@
#include "llvm/IntrinsicInst.h"
#include "llvm/Function.h"
#include "llvm/Analysis/AliasAnalysis.h"
+#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/MemoryBuiltins.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/STLExtras.h"
@@ -716,7 +717,8 @@
/// PHITranslateForPred - Given a computation that satisfied the
/// isPHITranslatable predicate, see if we can translate the computation into
/// the specified predecessor block. If so, return that value.
-static Value *PHITranslateForPred(Instruction *Inst, BasicBlock *Pred) {
+static Value *PHITranslateForPred(Instruction *Inst, BasicBlock *Pred,
+ const TargetData *TD) {
if (PHINode *PN = dyn_cast<PHINode>(Inst))
return PN->getIncomingValueForBlock(Pred);
@@ -751,7 +753,9 @@
GEPOps.back() = APHIOp = PN->getIncomingValueForBlock(Pred);
}
- // TODO: Simplify the GEP to handle 'gep x, 0' -> x etc.
+ // Simplify the GEP to handle 'gep x, 0' -> x etc.
+ if (Value *V = SimplifyGEPInst(&GEPOps[0], GEPOps.size(), TD))
+ return V;
// Scan to see if we have this GEP available.
for (Value::use_iterator UI = APHIOp->use_begin(), E = APHIOp->use_end();
@@ -926,7 +930,7 @@
for (BasicBlock **PI = PredCache->GetPreds(BB); *PI; ++PI) {
BasicBlock *Pred = *PI;
- Value *PredPtr = PHITranslateForPred(PtrInst, Pred);
+ Value *PredPtr = PHITranslateForPred(PtrInst, Pred, TD);
// If PHI translation fails, bail out.
if (PredPtr == 0)