commit 1e0edbf03ce31ab633e613f4b1b744f131858681
author Matt Arsenault <Matthew.Arsenault@amd.com> Wed Jan 11 00:33:24 2017 +0000
committer Matt Arsenault <Matthew.Arsenault@amd.com> Wed Jan 11 00:33:24 2017 +0000
tree 7d4856b98fca5e5ccabbf58da513283e9259fdf0
parent 1b31646465810af373693af1a146e2520c79bd78

InstSimplify: Eliminate fabs on known positive

llvm-svn: 291624

llvm/lib/Analysis/InstructionSimplify.cpp

diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 8da2f09..73dcd71 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -4308,10 +4308,21 @@
     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 (SignBitMustBeZero(*ArgBegin, Q.TLI))
+        return *ArgBegin;
+    }
+    default:
+      break;
+    }
+  }
 
   return nullptr;
 }