From 117feba971a020653fef3d6d61a16345355b83fd Mon Sep 17 00:00:00 2001
From: Duncan Sands <baldrick@free.fr>
Date: Wed, 18 May 2011 07:13:41 +0000
Subject: [PATCH] Teach getCastOpcode about element-by-element vector casts. 
 For example, "trunc" can be used to turn a <4 x i64> into a <4 x i32> but
 getCastOpcode would assert if you passed these types to it.  Note that this
 strictly extends the previous functionality: if getCastOpcode previously
 accepted two vector types (i.e. didn't assert) then it still will and returns
 the same opcode (BitCast).  That's because before it would only accept
 vectors with the same bitwidth, and the new code only touches vectors with
 the same length.  However if two vectors have both the same bitwidth and the
 same length then their element types have the same bitwidth, so the new logic
 will return BitCast as before.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@131530 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/VMCore/Instructions.cpp           | 29 +++++++++++++++++++++++----
 unittests/VMCore/InstructionsTest.cpp |  8 ++++++++
 2 files changed, 33 insertions(+), 4 deletions(-)

diff --git a/lib/VMCore/Instructions.cpp b/lib/VMCore/Instructions.cpp
index 61da9b6b8e0..af1492d356a 100644
--- a/lib/VMCore/Instructions.cpp
+++ b/lib/VMCore/Instructions.cpp
@@ -2254,6 +2254,14 @@ bool CastInst::isCastable(const Type *SrcTy, const Type *DestTy) {
   if (SrcTy == DestTy)
     return true;
 
+  if (const VectorType *SrcVecTy = dyn_cast<VectorType>(SrcTy))
+    if (const VectorType *DestVecTy = dyn_cast<VectorType>(DestTy))
+      if (SrcVecTy->getNumElements() == DestVecTy->getNumElements()) {
+        // An element by element cast.  Valid if casting the elements is valid.
+        SrcTy = SrcVecTy->getElementType();
+        DestTy = DestVecTy->getElementType();
+      }
+
   // Get the bit sizes, we'll need these
   unsigned SrcBits = SrcTy->getScalarSizeInBits();   // 0 for ptr
   unsigned DestBits = DestTy->getScalarSizeInBits(); // 0 for ptr
@@ -2322,14 +2330,27 @@ bool CastInst::isCastable(const Type *SrcTy, const Type *DestTy) {
 Instruction::CastOps
 CastInst::getCastOpcode(
   const Value *Src, bool SrcIsSigned, const Type *DestTy, bool DestIsSigned) {
-  // Get the bit sizes, we'll need these
   const Type *SrcTy = Src->getType();
-  unsigned SrcBits = SrcTy->getScalarSizeInBits();   // 0 for ptr
-  unsigned DestBits = DestTy->getScalarSizeInBits(); // 0 for ptr
 
   assert(SrcTy->isFirstClassType() && DestTy->isFirstClassType() &&
          "Only first class types are castable!");
 
+  if (SrcTy == DestTy)
+    return BitCast;
+
+  if (const VectorType *SrcVecTy = dyn_cast<VectorType>(SrcTy))
+    if (const VectorType *DestVecTy = dyn_cast<VectorType>(DestTy))
+      if (SrcVecTy->getNumElements() == DestVecTy->getNumElements()) {
+        // An element by element cast.  Find the appropriate opcode based on the
+        // element types.
+        SrcTy = SrcVecTy->getElementType();
+        DestTy = DestVecTy->getElementType();
+      }
+
+  // Get the bit sizes, we'll need these
+  unsigned SrcBits = SrcTy->getScalarSizeInBits();   // 0 for ptr
+  unsigned DestBits = DestTy->getScalarSizeInBits(); // 0 for ptr
+
   // Run through the possibilities ...
   if (DestTy->isIntegerTy()) {                      // Casting to integral
     if (SrcTy->isIntegerTy()) {                     // Casting from integral
@@ -2384,7 +2405,7 @@ CastInst::getCastOpcode(
     if (const VectorType *SrcPTy = dyn_cast<VectorType>(SrcTy)) {
       assert(DestPTy->getBitWidth() == SrcPTy->getBitWidth() &&
              "Casting vector to vector of different widths");
-      SrcPTy = NULL;
+      (void)SrcPTy;
       return BitCast;                             // vector -> vector
     } else if (DestPTy->getBitWidth() == SrcBits) {
       return BitCast;                               // float/int -> vector
diff --git a/unittests/VMCore/InstructionsTest.cpp b/unittests/VMCore/InstructionsTest.cpp
index 8edcce40cba..9624b816a8d 100644
--- a/unittests/VMCore/InstructionsTest.cpp
+++ b/unittests/VMCore/InstructionsTest.cpp
@@ -114,11 +114,19 @@ TEST(InstructionsTest, CastInst) {
   const Type* Int8Ty = Type::getInt8Ty(C);
   const Type* Int64Ty = Type::getInt64Ty(C);
   const Type* V8x8Ty = VectorType::get(Int8Ty, 8);
+  const Type* V8x64Ty = VectorType::get(Int64Ty, 8);
   const Type* X86MMXTy = Type::getX86_MMXTy(C);
 
+  const Constant* c8 = Constant::getNullValue(V8x8Ty);
+  const Constant* c64 = Constant::getNullValue(V8x64Ty);
+
   EXPECT_TRUE(CastInst::isCastable(V8x8Ty, X86MMXTy));
   EXPECT_TRUE(CastInst::isCastable(X86MMXTy, V8x8Ty));
   EXPECT_FALSE(CastInst::isCastable(Int64Ty, X86MMXTy));
+  EXPECT_TRUE(CastInst::isCastable(V8x64Ty, V8x8Ty));
+  EXPECT_TRUE(CastInst::isCastable(V8x8Ty, V8x64Ty));
+  EXPECT_EQ(CastInst::getCastOpcode(c64, true, V8x8Ty, true), CastInst::Trunc);
+  EXPECT_EQ(CastInst::getCastOpcode(c8, true, V8x64Ty, true), CastInst::SExt);
 }
 
 }  // end anonymous namespace
-- 
2.34.1