From 1c9a9f255c5064ba87e2075d11bd007c3b99ae34 Mon Sep 17 00:00:00 2001
From: Simon Pilgrim <llvm-dev@redking.me.uk>
Date: Sun, 24 Apr 2016 17:57:27 +0000
Subject: [PATCH] [InstCombine] Avoid updating argument demanded elements in
 separate passes.

As discussed on D17490, we should attempt to update an intrinsic's arguments demanded elements in one pass if we can.

llvm-svn: 267355
---
 .../Transforms/InstCombine/InstCombineCalls.cpp    | 22 +++++++++++++++-------
 1 file changed, 15 insertions(+), 7 deletions(-)

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index 763e5aa..3c02d66 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -1406,17 +1406,20 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) {
   case Intrinsic::x86_sse2_ucomineq_sd: {
     // These intrinsics only demand the 0th element of their input vectors. If
     // we can simplify the input based on that, do so now.
+    bool MadeChange = false;
     Value *Arg0 = II->getArgOperand(0);
     Value *Arg1 = II->getArgOperand(1);
     unsigned VWidth = Arg0->getType()->getVectorNumElements();
     if (Value *V = SimplifyDemandedVectorEltsLow(Arg0, VWidth, 1)) {
       II->setArgOperand(0, V);
-      return II;
+      MadeChange = true;
     }
     if (Value *V = SimplifyDemandedVectorEltsLow(Arg1, VWidth, 1)) {
       II->setArgOperand(1, V);
-      return II;
+      MadeChange = true;
     }
+    if (MadeChange)
+      return II;
     break;
   }
 
@@ -1531,14 +1534,17 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) {
 
     // EXTRQ only uses the lowest 64-bits of the first 128-bit vector
     // operands and the lowest 16-bits of the second.
+    bool MadeChange = false;
     if (Value *V = SimplifyDemandedVectorEltsLow(Op0, VWidth0, 1)) {
       II->setArgOperand(0, V);
-      return II;
+      MadeChange = true;
     }
     if (Value *V = SimplifyDemandedVectorEltsLow(Op1, VWidth1, 2)) {
       II->setArgOperand(1, V);
-      return II;
+      MadeChange = true;
     }
+    if (MadeChange)
+      return II;
     break;
   }
 
@@ -1626,15 +1632,17 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) {
 
     // INSERTQI only uses the lowest 64-bits of the first two 128-bit vector
     // operands.
+    bool MadeChange = false;
     if (Value *V = SimplifyDemandedVectorEltsLow(Op0, VWidth0, 1)) {
       II->setArgOperand(0, V);
-      return II;
+      MadeChange = true;
     }
-
     if (Value *V = SimplifyDemandedVectorEltsLow(Op1, VWidth1, 1)) {
       II->setArgOperand(1, V);
-      return II;
+      MadeChange = true;
     }
+    if (MadeChange)
+      return II;
     break;
   }
 
-- 
2.7.4