[InstSimplify] Fold gep (gep V, C), (xor V, -1) to C-1
llvm-svn: 278779
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 95273a7..3a1b272 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -3645,7 +3645,6 @@
}
}
- // gep (gep V, C), (sub 0, V) -> C
if (Q.DL.getTypeAllocSize(LastType) == 1 &&
all_of(Ops.slice(1).drop_back(1),
[](Value *Idx) { return match(Idx, m_Zero()); })) {
@@ -3657,11 +3656,18 @@
Ops[0]->stripAndAccumulateInBoundsConstantOffsets(Q.DL,
BasePtrOffset);
+ // gep (gep V, C), (sub 0, V) -> C
if (match(Ops.back(),
m_Sub(m_Zero(), m_PtrToInt(m_Specific(StrippedBasePtr))))) {
auto *CI = ConstantInt::get(GEPTy->getContext(), BasePtrOffset);
return ConstantExpr::getIntToPtr(CI, GEPTy);
}
+ // gep (gep V, C), (xor V, -1) -> C-1
+ if (match(Ops.back(),
+ m_Xor(m_PtrToInt(m_Specific(StrippedBasePtr)), m_AllOnes()))) {
+ auto *CI = ConstantInt::get(GEPTy->getContext(), BasePtrOffset - 1);
+ return ConstantExpr::getIntToPtr(CI, GEPTy);
+ }
}
}