From 1c9fe0361b3f9f5c814ce761b97ecd11637a1d7d Mon Sep 17 00:00:00 2001
From: Nadav Rotem <nadav.rotem@intel.com>
Date: Sat, 20 Aug 2011 14:02:29 +0000
Subject: [PATCH] Add constant folding support for bitcasts of splat vectors to
 integers.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@138206 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Analysis/ConstantFolding.cpp       | 12 ++++++++++--
 test/Transforms/InstCombine/bitcast.ll | 10 ++++++++++
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/lib/Analysis/ConstantFolding.cpp b/lib/Analysis/ConstantFolding.cpp
index d74d7e806e6..7a8c703040c 100644
--- a/lib/Analysis/ConstantFolding.cpp
+++ b/lib/Analysis/ConstantFolding.cpp
@@ -46,7 +46,16 @@ using namespace llvm;
 static Constant *FoldBitCast(Constant *C, Type *DestTy,
                              const TargetData &TD) {
   
-  // This only handles casts to vectors currently.
+  ConstantVector *CV = dyn_cast<ConstantVector>(C);
+  IntegerType *IntVTy = dyn_cast<IntegerType>(DestTy);
+  // When casting vectors to scalar integers, catch the
+  // obvious splat cases.
+  if (IntVTy && CV) {
+    if (CV->isNullValue()) return ConstantInt::getNullValue(IntVTy);
+    if (CV->isAllOnesValue()) return ConstantInt::getAllOnesValue(IntVTy);
+  }
+  
+  // The code below only handles casts to vectors currently.
   VectorType *DestVTy = dyn_cast<VectorType>(DestTy);
   if (DestVTy == 0)
     return ConstantExpr::getBitCast(C, DestTy);
@@ -59,7 +68,6 @@ static Constant *FoldBitCast(Constant *C, Type *DestTy,
   }
   
   // If this is a bitcast from constant vector -> vector, fold it.
-  ConstantVector *CV = dyn_cast<ConstantVector>(C);
   if (CV == 0)
     return ConstantExpr::getBitCast(C, DestTy);
   
diff --git a/test/Transforms/InstCombine/bitcast.ll b/test/Transforms/InstCombine/bitcast.ll
index 0718b8a3aee..b0630d27254 100644
--- a/test/Transforms/InstCombine/bitcast.ll
+++ b/test/Transforms/InstCombine/bitcast.ll
@@ -1,5 +1,8 @@
 ; RUN: opt < %s -instcombine -S | FileCheck %s
 
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64"
+target triple = "x86_64-apple-darwin10.0.0"
+
 ; Bitcasts between vectors and scalars are valid.
 ; PR4487
 define i32 @test1(i64 %a) {
@@ -103,3 +106,10 @@ define <2 x float> @test6(float %A){
 ; CHECK-NEXT: insertelement <2 x float> <float 4.200000e+01, float undef>, float %A, i32 1
 ; CHECK: ret
 }
+
+define i64 @ISPC0(i64 %in) {
+  %out = and i64 %in, xor (i64 bitcast (<4 x i16> <i16 -1, i16 -1, i16 -1, i16 -1> to i64), i64 -1)
+  ret i64 %out
+; CHECK: @ISPC0
+; CHECK: ret i64 0
+}