Fix bug introduced with 6f34839 (poison flags on floating point ops)

The newly introduced API for checking whether poison comes solely from flags which can be dropped was out of sync.  This was noticed by a reviewer post commit.

For the moment, disable the floating point flags.  In a follow up change, I plan to add support in dropPoisonGeneratingFlags, but that deserves to be a change of it's own.

diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index e5b1b24..ece7c88 100644 (file)
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -4959,11 +4959,14 @@ static bool canCreateUndefOrPoison(const Operator *Op, bool PoisonOnly,
     if (const auto *ExactOp = dyn_cast<PossiblyExactOperator>(Op))
       if (ExactOp->isExact())
         return true;
-    if (const auto *FP = dyn_cast<FPMathOperator>(Op)) {
-      auto FMF = FP->getFastMathFlags();
-      if (FMF.noNaNs() || FMF.noInfs())
-        return true;
-    }
+  }
+
+  // TODO: this should really be under the ConsiderFlags block, but currently
+  // these are not dropped by dropPoisonGeneratingFlags
+  if (const auto *FP = dyn_cast<FPMathOperator>(Op)) {
+    auto FMF = FP->getFastMathFlags();
+    if (FMF.noNaNs() || FMF.noInfs())
+      return true;
   }
 
   unsigned Opcode = Op->getOpcode();

diff --git a/llvm/test/Transforms/InstCombine/freeze.ll b/llvm/test/Transforms/InstCombine/freeze.ll
index 981d671..a2c7880 100644 (file)
--- a/llvm/test/Transforms/InstCombine/freeze.ll
+++ b/llvm/test/Transforms/InstCombine/freeze.ll
@@ -374,3 +374,14 @@ define i8* @propagate_drop_gep2(i8* %arg, i64 %unknown) {
   ret i8* %v1.fr
 }
 
+
+define float @propagate_drop_fadd(float %arg) {
+; CHECK-LABEL: @propagate_drop_fadd(
+; CHECK-NEXT:    [[V1:%.*]] = fadd ninf float [[ARG:%.*]], 2.000000e+00
+; CHECK-NEXT:    [[V1_FR:%.*]] = freeze float [[V1]]
+; CHECK-NEXT:    ret float [[V1_FR]]
+;
+  %v1 = fadd ninf float %arg, 2.0
+  %v1.fr = freeze float %v1
+  ret float %v1.fr
+}