[PATCH] D139312: ValueTracking: Teach CannotBeOrderedLessThanZero about copysign

[Matt Arsenault via Phabricator via llvm-commits]

arsenm updated this revision to Diff 480156.
arsenm added a comment.

The whole reason I used sqrt in the test was to test -0 and I still got it wrong


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D139312/new/

https://reviews.llvm.org/D139312

Files:
  llvm/lib/Analysis/ValueTracking.cpp
  llvm/test/Transforms/InstSimplify/floating-point-arithmetic.ll


Index: llvm/test/Transforms/InstSimplify/floating-point-arithmetic.ll
===================================================================
--- llvm/test/Transforms/InstSimplify/floating-point-arithmetic.ll
+++ llvm/test/Transforms/InstSimplify/floating-point-arithmetic.ll
@@ -279,6 +279,7 @@
 declare float @llvm.fabs.f32(float)
 declare float @llvm.canonicalize.f32(float)
 declare float @llvm.arithmetic.fence.f32(float)
+declare float @llvm.copysign.f32(float, float)
 declare <2 x float> @llvm.fabs.v2f32(<2 x float>)
 declare float @llvm.sqrt.f32(float)
 declare float @llvm.maxnum.f32(float, float)
@@ -955,3 +956,37 @@
   %cmp = fcmp nnan oge float %known.positive, 0.0
   ret i1 %cmp
 }
+
+define i1 @copysign_known_positive_maybe_neg0(float %unknown, float %sign) {
+; CHECK-LABEL: @copysign_known_positive_maybe_neg0(
+; CHECK-NEXT:    [[SQRT:%.*]] = call nnan ninf float @llvm.sqrt.f32(float [[SIGN:%.*]])
+; CHECK-NEXT:    [[COPYSIGN:%.*]] = call float @llvm.copysign.f32(float [[UNKNOWN:%.*]], float [[SQRT]])
+; CHECK-NEXT:    [[CMP:%.*]] = fcmp nnan oge float [[COPYSIGN]], 0.000000e+00
+; CHECK-NEXT:    ret i1 [[CMP]]
+;
+  %sqrt = call ninf nnan float @llvm.sqrt.f32(float %sign)
+  %copysign = call float @llvm.copysign.f32(float %unknown, float %sqrt)
+  %cmp = fcmp nnan oge float %copysign, 0.0
+  ret i1 %cmp
+}
+
+define i1 @copysign_known_positive(float %unknown, float %sign) {
+; CHECK-LABEL: @copysign_known_positive(
+; CHECK-NEXT:    ret i1 true
+;
+  %sqrt = call ninf nnan nsz float @llvm.sqrt.f32(float %sign)
+  %copysign = call float @llvm.copysign.f32(float %unknown, float %sqrt)
+  %cmp = fcmp nnan oge float %copysign, 0.0
+  ret i1 %cmp
+}
+
+define i1 @copysign_unknown_positive(float %unknown, float %unknown.sign) {
+; CHECK-LABEL: @copysign_unknown_positive(
+; CHECK-NEXT:    [[COPYSIGN:%.*]] = call float @llvm.copysign.f32(float [[UNKNOWN:%.*]], float [[UNKNOWN_SIGN:%.*]])
+; CHECK-NEXT:    [[CMP:%.*]] = fcmp nnan oge float [[COPYSIGN]], 0.000000e+00
+; CHECK-NEXT:    ret i1 [[CMP]]
+;
+  %copysign = call float @llvm.copysign.f32(float %unknown, float %unknown.sign)
+  %cmp = fcmp nnan oge float %copysign, 0.0
+  ret i1 %cmp
+}
Index: llvm/lib/Analysis/ValueTracking.cpp
===================================================================
--- llvm/lib/Analysis/ValueTracking.cpp
+++ llvm/lib/Analysis/ValueTracking.cpp
@@ -3694,7 +3694,10 @@
     case Intrinsic::exp2:
     case Intrinsic::fabs:
       return true;
-
+    case Intrinsic::copysign:
+      // Only the sign operand matters.
+      return cannotBeOrderedLessThanZeroImpl(I->getOperand(1), TLI, true,
+                                             Depth + 1);
     case Intrinsic::sqrt:
       // sqrt(x) is always >= -0 or NaN.  Moreover, sqrt(x) == -0 iff x == -0.
       if (!SignBitOnly)


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