[PATCH] D147939: ValueTracking: Handle fptrunc in computeKnownFPClass

[Matt Arsenault via Phabricator via llvm-commits]

arsenm updated this revision to Diff 513378.

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D147939/new/

https://reviews.llvm.org/D147939

Files:
  llvm/lib/Analysis/ValueTracking.cpp
  llvm/test/Transforms/Attributor/nofpclass-fptrunc.ll


Index: llvm/test/Transforms/Attributor/nofpclass-fptrunc.ll
===================================================================
--- llvm/test/Transforms/Attributor/nofpclass-fptrunc.ll
+++ llvm/test/Transforms/Attributor/nofpclass-fptrunc.ll
@@ -12,7 +12,7 @@
 }
 
 define float @ret_fptrunc_nonan(double nofpclass(nan) %arg0) {
-; CHECK-LABEL: define float @ret_fptrunc_nonan
+; CHECK-LABEL: define nofpclass(nan) float @ret_fptrunc_nonan
 ; CHECK-SAME: (double nofpclass(nan) [[ARG0:%.*]]) #[[ATTR0]] {
 ; CHECK-NEXT:    [[EXT:%.*]] = fptrunc double [[ARG0]] to float
 ; CHECK-NEXT:    ret float [[EXT]]
@@ -102,7 +102,7 @@
 }
 
 define float @ret_fptrunc_nonan_noinf(double nofpclass(nan inf) %arg0) {
-; CHECK-LABEL: define float @ret_fptrunc_nonan_noinf
+; CHECK-LABEL: define nofpclass(nan) float @ret_fptrunc_nonan_noinf
 ; CHECK-SAME: (double nofpclass(nan inf) [[ARG0:%.*]]) #[[ATTR0]] {
 ; CHECK-NEXT:    [[EXT:%.*]] = fptrunc double [[ARG0]] to float
 ; CHECK-NEXT:    ret float [[EXT]]
Index: llvm/lib/Analysis/ValueTracking.cpp
===================================================================
--- llvm/lib/Analysis/ValueTracking.cpp
+++ llvm/lib/Analysis/ValueTracking.cpp
@@ -4641,6 +4641,19 @@
       Known.SignBit = std::nullopt;
     break;
   }
+  case Instruction::FPTrunc: {
+    if ((InterestedClasses & fcNan) == fcNone)
+      break;
+
+    KnownFPClass KnownSrc;
+    computeKnownFPClass(Op->getOperand(0), DemandedElts,
+                        InterestedClasses, KnownSrc, Depth + 1, Q, TLI);
+    if (KnownSrc.isKnownNeverNaN())
+      Known.knownNot(fcNan);
+
+    // Infinity needs a range check.
+    break;
+  }
   case Instruction::SIToFP:
   case Instruction::UIToFP: {
     // Cannot produce nan


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