Fix the inline cost calculation to take into account instructions
which cannot be folded even if they have constant operands. Significantly
helps if_spppsubr.c attached to PR4573.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@76285 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Utils/InlineCost.cpp b/lib/Transforms/Utils/InlineCost.cpp
index 87aff01..5fe85e6 100644
--- a/lib/Transforms/Utils/InlineCost.cpp
+++ b/lib/Transforms/Utils/InlineCost.cpp
@@ -42,6 +42,13 @@
// Figure out if this instruction will be removed due to simple constant
// propagation.
Instruction &Inst = cast<Instruction>(**UI);
+
+ // We can't constant propagate instructions which have effects or
+ // read memory.
+ if (Inst.mayReadFromMemory() || Inst.mayHaveSideEffects() ||
+ isa<AllocationInst>(Inst))
+ continue;
+
bool AllOperandsConstant = true;
for (unsigned i = 0, e = Inst.getNumOperands(); i != e; ++i)
if (!isa<Constant>(Inst.getOperand(i)) && Inst.getOperand(i) != V) {