[llvm] 656b52a - ValueTracking: Handle non-splat vectors in computeKnownFPClass

[Matt Arsenault via llvm-commits]

Author: Matt Arsenault
Date: 2023-04-14T17:41:26-04:00
New Revision: 656b52a6c61e15dfbd5969417d66fcaf0e730ce1

URL: https://github.com/llvm/llvm-project/commit/656b52a6c61e15dfbd5969417d66fcaf0e730ce1
DIFF: https://github.com/llvm/llvm-project/commit/656b52a6c61e15dfbd5969417d66fcaf0e730ce1.diff

LOG: ValueTracking: Handle non-splat vectors in computeKnownFPClass

Avoids some regressions when the implementation of isKnownNeverNaN is
replaced with computeKnownFPClass.

Added: 
    

Modified: 
    llvm/lib/Analysis/ValueTracking.cpp
    llvm/test/Transforms/Attributor/nofpclass.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index b4ff5940201d..51f88945c532 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -4362,12 +4362,38 @@ void computeKnownFPClass(const Value *V, const APInt &DemandedElts,
 
   assert(Depth <= MaxAnalysisRecursionDepth && "Limit Search Depth");
 
-  const APFloat *C;
-  if (match(V, m_APFloat(C))) {
-    // We know all of the classes for a scalar constant or a splat vector
-    // constant!
-    Known.KnownFPClasses = C->classify();
-    Known.SignBit = C->isNegative();
+  if (auto *CFP = dyn_cast_or_null<ConstantFP>(V)) {
+    Known.KnownFPClasses = CFP->getValueAPF().classify();
+    Known.SignBit = CFP->isNegative();
+    return;
+  }
+
+  // Try to handle fixed width vector constants
+  auto *VFVTy = dyn_cast<FixedVectorType>(V->getType());
+  const Constant *CV = dyn_cast<Constant>(V);
+  if (VFVTy && CV) {
+    Known.KnownFPClasses = fcNone;
+
+    // For vectors, verify that each element is not NaN.
+    unsigned NumElts = VFVTy->getNumElements();
+    for (unsigned i = 0; i != NumElts; ++i) {
+      Constant *Elt = CV->getAggregateElement(i);
+      if (!Elt) {
+        Known = KnownFPClass();
+        return;
+      }
+      if (isa<UndefValue>(Elt))
+        continue;
+      auto *CElt = dyn_cast<ConstantFP>(Elt);
+      if (!CElt) {
+        Known = KnownFPClass();
+        return;
+      }
+
+      KnownFPClass KnownElt{CElt->getValueAPF().classify(), CElt->isNegative()};
+      Known |= KnownElt;
+    }
+
     return;
   }
 

diff  --git a/llvm/test/Transforms/Attributor/nofpclass.ll b/llvm/test/Transforms/Attributor/nofpclass.ll
index a363933fcfe9..52c9c2e12fdb 100644
--- a/llvm/test/Transforms/Attributor/nofpclass.ll
+++ b/llvm/test/Transforms/Attributor/nofpclass.ll
@@ -97,7 +97,7 @@ define <2 x double> @returned_strange_constant_vector_elt() {
 
 ; Test a vector element that's an undef/poison
 define <3 x double> @returned_undef_constant_vector_elt() {
-; CHECK-LABEL: define <3 x double> @returned_undef_constant_vector_elt() {
+; CHECK-LABEL: define nofpclass(nan inf pzero sub norm) <3 x double> @returned_undef_constant_vector_elt() {
 ; CHECK-NEXT:    call void @unknown()
 ; CHECK-NEXT:    ret <3 x double> <double -0.000000e+00, double poison, double undef>
 ;
@@ -106,7 +106,7 @@ define <3 x double> @returned_undef_constant_vector_elt() {
 }
 
 define <2 x double> @returned_qnan_zero_vector() {
-; CHECK-LABEL: define noundef <2 x double> @returned_qnan_zero_vector() {
+; CHECK-LABEL: define noundef nofpclass(snan inf nzero sub norm) <2 x double> @returned_qnan_zero_vector() {
 ; CHECK-NEXT:    call void @unknown()
 ; CHECK-NEXT:    ret <2 x double> <double 0x7FF8000000000000, double 0.000000e+00>
 ;