[PATCH] D43789: [ValueTracking] Teach cannotBeOrderedLessThanZeroImpl to look through ExtractElement.

[Craig Topper via Phabricator via llvm-commits]

craig.topper created this revision.
craig.topper added reviewers: spatel, arsenm.
Herald added a subscriber: wdng.

This is similar to what's done in computeKnownBits and computeSignBits. Don't do anything fancy just collect information valid for any element.


Repository:
  rL LLVM

https://reviews.llvm.org/D43789

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


Index: test/Transforms/InstSimplify/floating-point-arithmetic.ll
===================================================================
--- test/Transforms/InstSimplify/floating-point-arithmetic.ll
+++ test/Transforms/InstSimplify/floating-point-arithmetic.ll
@@ -406,3 +406,17 @@
   %fabs = call float @llvm.fabs.f32(float %sqrt)
   ret float %fabs
 }
+
+define float @fabs_select_positive_constants_vector_extract(i32 %c) {
+; CHECK-LABEL: @fabs_select_positive_constants_vector_extract(
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i32 [[C:%.*]], 0
+; CHECK-NEXT:    [[SELECT:%.*]] = select i1 [[CMP]], <2 x float> <float 1.000000e+00, float 1.000000e+00>, <2 x float> <float 2.000000e+00, float 2.000000e+00>
+; CHECK-NEXT:    [[EXTRACT:%.*]] = extractelement <2 x float> [[SELECT]], i32 0
+; CHECK-NEXT:    ret float [[EXTRACT]]
+;
+  %cmp = icmp eq i32 %c, 0
+  %select = select i1 %cmp, <2 x float> <float 1.0, float 1.0>, <2 x float> <float 2.0, float 2.0>
+  %extract = extractelement <2 x float> %select, i32 0
+  %fabs = call float @llvm.fabs.f32(float %extract)
+  ret float %fabs
+}
Index: lib/Analysis/ValueTracking.cpp
===================================================================
--- lib/Analysis/ValueTracking.cpp
+++ lib/Analysis/ValueTracking.cpp
@@ -2783,6 +2783,12 @@
     // Widening/narrowing never change sign.
     return cannotBeOrderedLessThanZeroImpl(I->getOperand(0), TLI, SignBitOnly,
                                            Depth + 1);
+  case Instruction::ExtractElement:
+    // Look through extract element. At the moment we keep this simple and skip
+    // tracking the specific element. But at least we might find information
+    // valid for all elements of the vector.
+    return cannotBeOrderedLessThanZeroImpl(I->getOperand(0), TLI, SignBitOnly,
+                                           Depth + 1);
   case Instruction::Call:
     const auto *CI = cast<CallInst>(I);
     Intrinsic::ID IID = getIntrinsicForCallSite(CI, TLI);


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