Reland r301880(!): "[InstSimplify] Handle selects of GEPs with 0 offset"
I was reminded today that this patch got reverted in r301885. I can no
longer reproduce the failure that caused the revert locally (...almost
one year later), and the patch applied pretty cleanly, so I guess we'll
see if the bots still get angry about it.
The original breakage was InstSimplify complaining (in "assertion
failed" form) about getting passed some crazy IR when running `ninja
check-sanitizer`. I'm unable to find traces of what, exactly, said crazy
IR was. I suppose we'll find out pretty soon if that's still the case.
:)
Original commit:
Author: gbiv
Date: Mon May 1 18:12:08 2017
New Revision: 301880
URL: http://llvm.org/viewvc/llvm-project?rev=301880&view=rev
Log:
[InstSimplify] Handle selects of GEPs with 0 offset
In particular (since it wouldn't fit nicely in the summary):
(select (icmp eq V 0) P (getelementptr P V)) -> (getelementptr P V)
Differential Revision: https://reviews.llvm.org/D31435
llvm-svn: 330667
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 1e62b9d..25c38c0 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -62,6 +62,8 @@
static Value *SimplifyXorInst(Value *, Value *, const SimplifyQuery &, unsigned);
static Value *SimplifyCastInst(unsigned, Value *, Type *,
const SimplifyQuery &, unsigned);
+static Value *SimplifyGEPInst(Type *, ArrayRef<Value *>, const SimplifyQuery &,
+ unsigned);
/// For a boolean type or a vector of boolean type, return false or a vector
/// with every element false.
@@ -3528,6 +3530,17 @@
}
}
+ // Same for GEPs.
+ if (auto *GEP = dyn_cast<GetElementPtrInst>(I)) {
+ if (MaxRecurse) {
+ SmallVector<Value *, 8> NewOps(GEP->getNumOperands());
+ transform(GEP->operands(), NewOps.begin(),
+ [&](Value *V) { return V == Op ? RepOp : V; });
+ return SimplifyGEPInst(GEP->getSourceElementType(), NewOps, Q,
+ MaxRecurse - 1);
+ }
+ }
+
// TODO: We could hand off more cases to instsimplify here.
// If all operands are constant after substituting Op for RepOp then we can