[PATCH] D27932: InstSimplify: Eliminate fabs on known positive

[Matt Arsenault via Phabricator via llvm-commits]

arsenm created this revision.
arsenm added a subscriber: llvm-commits.
Herald added a subscriber: wdng.

https://reviews.llvm.org/D27932

Files:
  lib/Analysis/InstructionSimplify.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
@@ -103,3 +103,44 @@
   ret float %7
 }
 
+declare float @llvm.fabs.f32(float)
+
+; CHECK-LABEL: @fabs_select_positive_constants(
+; CHECK: %select = select i1 %cmp, float 1.000000e+00, float 2.000000e+00
+; CHECK-NEXT: ret float %select
+define float @fabs_select_positive_constants(i32 %c) {
+  %cmp = icmp eq i32 %c, 0
+  %select = select i1 %cmp, float 1.0, float 2.0
+  %fabs = call float @llvm.fabs.f32(float %select)
+  ret float %fabs
+}
+
+; CHECK-LABEL: @fabs_select_constant_variable(
+; CHECK: %select = select i1 %cmp, float 1.000000e+00, float %x
+; CHECK-NEXT: %fabs = call float @llvm.fabs.f32(float %select)
+define float @fabs_select_constant_variable(i32 %c, float %x) {
+  %cmp = icmp eq i32 %c, 0
+  %select = select i1 %cmp, float 1.0, float %x
+  %fabs = call float @llvm.fabs.f32(float %select)
+  ret float %fabs
+}
+
+; CHECK-LABEL: @fabs_select_neg0_pos0(
+; CHECK: %select = select i1 %cmp, float -0.000000e+00, float 0.000000e+00
+; CHECK-NEXT: ret float %select
+define float @fabs_select_neg0_pos0(float addrspace(1)* %out, i32 %c) {
+  %cmp = icmp eq i32 %c, 0
+  %select = select i1 %cmp, float -0.0, float 0.0
+  %fabs = call float @llvm.fabs.f32(float %select)
+  ret float %fabs
+}
+
+; CHECK-LABEL: @fabs_select_neg0_neg1(
+; CHECK: %select = select i1 %cmp, float -0.000000e+00, float -1.000000e+00
+; CHECK: %fabs = call float @llvm.fabs.f32(float %select)
+define float @fabs_select_neg0_neg1(float addrspace(1)* %out, i32 %c) {
+  %cmp = icmp eq i32 %c, 0
+  %select = select i1 %cmp, float -0.0, float -1.0
+  %fabs = call float @llvm.fabs.f32(float %select)
+  ret float %fabs
+}
Index: lib/Analysis/InstructionSimplify.cpp
===================================================================
--- lib/Analysis/InstructionSimplify.cpp
+++ lib/Analysis/InstructionSimplify.cpp
@@ -4288,10 +4288,21 @@
     return nullptr;
 
   // Unary Ops
-  if (NumOperands == 1)
-    if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(*ArgBegin))
+  if (NumOperands == 1) {
+    if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(*ArgBegin)) {
       if (II->getIntrinsicID() == IID)
         return II;
+    }
+
+    switch (IID) {
+    case Intrinsic::fabs: {
+      if (CannotBeOrderedLessThanZero(*ArgBegin, Q.TLI))
+        return *ArgBegin;
+    }
+    default:
+      break;
+    }
+  }
 
   return nullptr;
 }


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