From 54e5db21e435b96a71033456a382e598fde53e49 Mon Sep 17 00:00:00 2001
From: Matt Arsenault <Matthew.Arsenault@amd.com>
Date: Fri, 10 Aug 2018 18:58:49 +0000
Subject: [PATCH] AMDGPU: Turn class x, p_zero|n_zero into fcmp oeq x, 0

The library does use this for some reason.

llvm-svn: 339461
---
 lib/Transforms/InstCombine/InstCombineCalls.cpp         | 9 +++++++++
 test/Transforms/InstCombine/AMDGPU/amdgcn-intrinsics.ll | 7 +++++++
 2 files changed, 16 insertions(+)

diff --git a/lib/Transforms/InstCombine/InstCombineCalls.cpp b/lib/Transforms/InstCombine/InstCombineCalls.cpp
index 310b87e931c..f0c4cebd7fd 100644
--- a/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -3195,6 +3195,15 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) {
       return replaceInstUsesWith(*II, FCmp);
     }
 
+    if (Mask == (N_ZERO | P_ZERO)) {
+      // Equivalent of == 0.
+      Value *FCmp = Builder.CreateFCmpOEQ(
+        Src0, ConstantFP::get(Src0->getType(), 0.0));
+
+      FCmp->takeName(II);
+      return replaceInstUsesWith(*II, FCmp);
+    }
+
     const ConstantFP *CVal = dyn_cast<ConstantFP>(Src0);
     if (!CVal) {
       if (isa<UndefValue>(Src0))
diff --git a/test/Transforms/InstCombine/AMDGPU/amdgcn-intrinsics.ll b/test/Transforms/InstCombine/AMDGPU/amdgcn-intrinsics.ll
index 1fad1d8f22e..e7b2fe39b30 100644
--- a/test/Transforms/InstCombine/AMDGPU/amdgcn-intrinsics.ll
+++ b/test/Transforms/InstCombine/AMDGPU/amdgcn-intrinsics.ll
@@ -457,6 +457,13 @@ define i1 @test_class_isnan_f32(float %x) nounwind {
   ret i1 %val
 }
 
+; CHECK-LABEL: @test_class_is_p0_n0_f32(
+; CHECK: %val = fcmp oeq float %x, 0.000000e+00
+define i1 @test_class_is_p0_n0_f32(float %x) nounwind {
+  %val = call i1 @llvm.amdgcn.class.f32(float %x, i32 96)
+  ret i1 %val
+}
+
 ; CHECK-LABEL: @test_constant_class_snan_test_snan_f64(
 ; CHECK: ret i1 true
 define i1 @test_constant_class_snan_test_snan_f64() nounwind {