[PATCH] D27937: InstCombine: Fold fabs on select of constants

[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/D27937

Files:
  lib/Transforms/InstCombine/InstCombineCalls.cpp
  test/Transforms/InstCombine/fabs.ll


Index: test/Transforms/InstCombine/fabs.ll
===================================================================
--- test/Transforms/InstCombine/fabs.ll
+++ test/Transforms/InstCombine/fabs.ll
@@ -98,3 +98,51 @@
 ; CHECK-NEXT: ret float %sq
 }
 
+; CHECK-LABEL: @fabs_select_constant_negative_positive(
+; CHECK: %fabs = select i1 %cmp, float 1.000000e+00, float 2.000000e+00
+; CHECK-NEXT: ret float %fabs
+define float @fabs_select_constant_negative_positive(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_positive_negative(
+; CHECK: %fabs = select i1 %cmp, float 1.000000e+00, float 2.000000e+00
+; CHECK-NEXT: ret float %fabs
+define float @fabs_select_constant_positive_negative(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_negative_negative(
+; CHECK: %fabs = select i1 %cmp, float 1.000000e+00, float 2.000000e+00
+; CHECK-NEXT: ret float %fabs
+define float @fabs_select_constant_negative_negative(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_neg0(
+; CHECK-NEXT: ret float 0.0
+define float @fabs_select_constant_neg0(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_var_constant_negative(
+; CHECK: %select = select i1 %cmp, float %x, float -1.000000e+00
+; CHECK: %fabs = call float @llvm.fabs.f32(float %select)
+define float @fabs_select_var_constant_negative(i32 %c, float %x) {
+  %cmp = icmp eq i32 %c, 0
+  %select = select i1 %cmp, float %x, float -1.0
+  %fabs = call float @llvm.fabs.f32(float %select)
+  ret float %fabs
+}
Index: lib/Transforms/InstCombine/InstCombineCalls.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -1599,6 +1599,18 @@
 
     break;
   }
+  case Intrinsic::fabs: {
+    Value *Cond;
+    Constant *LHS, *RHS;
+    if (match(II->getArgOperand(0),
+              m_Select(m_Value(Cond), m_Constant(LHS), m_Constant(RHS)))) {
+      CallInst *Call0 = Builder->CreateCall(II->getCalledFunction(), {LHS});
+      CallInst *Call1 = Builder->CreateCall(II->getCalledFunction(), {RHS});
+      return SelectInst::Create(Cond, Call0, Call1);
+    }
+
+    break;
+  }
   case Intrinsic::ppc_altivec_lvx:
   case Intrinsic::ppc_altivec_lvxl:
     // Turn PPC lvx -> load if the pointer is known aligned.


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