From 7aa18bf46ae5123f418f7316939a1b7d9f371ebc Mon Sep 17 00:00:00 2001
From: Nate Begeman <natebegeman@mac.com>
Date: Fri, 17 Dec 2010 23:12:19 +0000
Subject: Add vector versions of some existing scalar transforms to aid codegen
 in matching psign & pblend operations to the IR produced by clang/gcc for
 their C idioms.

llvm-svn: 122105
---
 llvm/lib/Analysis/ValueTracking.cpp | 7 +++++++
 1 file changed, 7 insertions(+)

(limited to 'llvm/lib/Analysis/ValueTracking.cpp')

diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 7506295..f8145cd 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -678,6 +678,13 @@ unsigned llvm::ComputeNumSignBits(Value *V, const TargetData *TD,
       Tmp += C->getZExtValue();
       if (Tmp > TyBits) Tmp = TyBits;
     }
+    // vector ashr X, <C, C, C, C>  -> adds C sign bits
+    if (ConstantVector *C = dyn_cast<ConstantVector>(U->getOperand(1))) {
+      if (ConstantInt *CI = dyn_cast_or_null<ConstantInt>(C->getSplatValue())) {
+        Tmp += CI->getZExtValue();
+        if (Tmp > TyBits) Tmp = TyBits;
+      }
+    }
     return Tmp;
   case Instruction::Shl:
     if (ConstantInt *C = dyn_cast<ConstantInt>(U->getOperand(1))) {
-- 
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