[X86][DAGCombiner] Skip x87 fp80 values in `combineFMulOrFDivWithIntPow2` (#128618)

f80 is not a valid IEEE floating-point type.
Closes https://github.com/llvm/llvm-project/issues/128528.

2 files changed, 10 insertions, 2 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index a83be13..6746a5d 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -17271,6 +17271,9 @@ SDValue DAGCombiner::visitFSUB(SDNode *N) {
 // prefer it.
 SDValue DAGCombiner::combineFMulOrFDivWithIntPow2(SDNode *N) {
   EVT VT = N->getValueType(0);
+  if (!APFloat::isIEEELikeFP(VT.getFltSemantics()))
+    return SDValue();
+
   SDValue ConstOp, Pow2Op;
 
   std::optional<int> Mantissa;
@@ -17297,8 +17300,8 @@ SDValue DAGCombiner::combineFMulOrFDivWithIntPow2(SDNode *N) {
 
       const APFloat &APF = CFP->getValueAPF();
 
-      // Make sure we have normal/ieee constant.
-      if (!APF.isNormal() || !APF.isIEEE())
+      // Make sure we have normal constant.
+      if (!APF.isNormal())
         return false;
 
       // Make sure the floats exponent is within the bounds that this transform
diff --git a/llvm/lib/Support/APFloat.cpp b/llvm/lib/Support/APFloat.cpp
index b0d92ae..cbee7f4 100644
--- a/llvm/lib/Support/APFloat.cpp
+++ b/llvm/lib/Support/APFloat.cpp
@@ -353,6 +353,11 @@ bool APFloatBase::semanticsHasNaN(const fltSemantics &semantics) {
   return semantics.nonFiniteBehavior != fltNonfiniteBehavior::FiniteOnly;
 }
 
+bool APFloatBase::isIEEELikeFP(const fltSemantics &semantics) {
+  // Keep in sync with Type::isIEEELikeFPTy
+  return SemanticsToEnum(semantics) <= S_IEEEquad;
+}
+
 bool APFloatBase::isRepresentableAsNormalIn(const fltSemantics &Src,
                                             const fltSemantics &Dst) {
   // Exponent range must be larger.