ValueTracking: Handle compare gt to -inf in class identification (#72086)

This apparently shows up somewhere in chromium. We also are missing a
canonicalization to an equality compare with inf.

1 files changed, 16 insertions, 4 deletions

diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 923ff04..dc3c90b 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -4181,8 +4181,14 @@ llvm::fcmpToClassTest(FCmpInst::Predicate Pred, const Function &F, Value *LHS,
     }
     case FCmpInst::FCMP_OGE:
     case FCmpInst::FCMP_ULT: {
-      if (ConstRHS->isNegative()) // TODO
-        return {nullptr, fcAllFlags};
+      if (ConstRHS->isNegative()) {
+        // fcmp oge x, -inf -> ~fcNan
+        // fcmp oge fabs(x), -inf -> ~fcNan
+        // fcmp ult x, -inf -> fcNan
+        // fcmp ult fabs(x), -inf -> fcNan
+        Mask = ~fcNan;
+        break;
+      }
 
       // fcmp oge fabs(x), +inf -> fcInf
       // fcmp oge x, +inf -> fcPosInf
@@ -4195,8 +4201,14 @@ llvm::fcmpToClassTest(FCmpInst::Predicate Pred, const Function &F, Value *LHS,
     }
     case FCmpInst::FCMP_OGT:
     case FCmpInst::FCMP_ULE: {
-      if (ConstRHS->isNegative())
-        return {nullptr, fcAllFlags};
+      if (ConstRHS->isNegative()) {
+        // fcmp ogt x, -inf -> fcmp one x, -inf
+        // fcmp ogt fabs(x), -inf -> fcmp ord x, x
+        // fcmp ule x, -inf -> fcmp ueq x, -inf
+        // fcmp ule fabs(x), -inf -> fcmp uno x, x
+        Mask = IsFabs ? ~fcNan : ~(fcNegInf | fcNan);
+        break;
+      }
 
       // No value is ordered and greater than infinity.
       Mask = fcNone;