[PATCH] D124150: [InstCombine] Handle more predicates for fold fcmp-of-copysign

[Chenbing.Zheng via Phabricator via llvm-commits]

Chenbing.Zheng created this revision.
Chenbing.Zheng added reviewers: spatel, RKSimon, benshi001, luismarques.
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This patch fold
copysign(non-zero constant, X) < 0.0 --> (bitcast X) < 0


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D124150

Files:
  llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
  llvm/test/Transforms/InstCombine/fcmp.ll


Index: llvm/test/Transforms/InstCombine/fcmp.ll
===================================================================
--- llvm/test/Transforms/InstCombine/fcmp.ll
+++ llvm/test/Transforms/InstCombine/fcmp.ll
@@ -605,12 +605,10 @@
   ret <2 x i1> %r
 }
 
-; TODO: Handle different predicates.
-
 define i1 @is_signbit_clear(double %x) {
 ; CHECK-LABEL: @is_signbit_clear(
-; CHECK-NEXT:    [[S:%.*]] = call double @llvm.copysign.f64(double -4.200000e+01, double [[X:%.*]])
-; CHECK-NEXT:    [[R:%.*]] = fcmp ogt double [[S]], 0.000000e+00
+; CHECK-NEXT:    [[TMP1:%.*]] = bitcast double [[X:%.*]] to i64
+; CHECK-NEXT:    [[R:%.*]] = icmp sgt i64 [[TMP1]], 0
 ; CHECK-NEXT:    ret i1 [[R]]
 ;
   %s = call double @llvm.copysign.f64(double -42.0, double %x)
Index: llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -6749,7 +6749,6 @@
   // Convert a sign-bit test of an FP value into a cast and integer compare.
   // TODO: Simplify if the copysign constant is 0.0 or NaN.
   // TODO: Handle non-zero compare constants.
-  // TODO: Handle other predicates.
   const APFloat *C;
   if (match(Op0, m_OneUse(m_Intrinsic<Intrinsic::copysign>(m_APFloat(C),
                                                            m_Value(X)))) &&
@@ -6764,6 +6763,12 @@
       return new ICmpInst(ICmpInst::ICMP_SLT, IntX,
                           ConstantInt::getNullValue(IntType));
     }
+    // copysign(non-zero constant, X) > 0.0 --> (bitcast X) > 0
+    if (Pred == FCmpInst::FCMP_OGT) {
+      Value *IntX = Builder.CreateBitCast(X, IntType);
+      return new ICmpInst(ICmpInst::ICMP_SGT, IntX,
+                          ConstantInt::getNullValue(IntType));
+    }
   }
 
   if (I.getType()->isVectorTy())


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