From 91abace4ef6fdfe01bcebfb8e90938e71f8a5c4f Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Wed, 1 Sep 2010 05:14:33 +0000
Subject: [PATCH] add a gross hack to work around a problem that Argiris
 reported on llvmdev: SRoA is introducing MMX datatypes like <1 x i64>, which
 then cause random problems because the X86 backend is producing mmx stuff
 without inserting proper emms calls.

In the short term, force off MMX datatypes.  In the long term,
the X86 backend should not select generic vector types to MMX
registers.  This is being worked on, but won't be done in time
for 2.8.  rdar://8380055


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@112696 91177308-0d34-0410-b5e6-96231b3b80d8
---
 .../Scalar/ScalarReplAggregates.cpp           | 31 +++++++++++++++----
 test/Transforms/ScalarRepl/vector_promote.ll  | 14 +++++++++
 2 files changed, 39 insertions(+), 6 deletions(-)

diff --git a/lib/Transforms/Scalar/ScalarReplAggregates.cpp b/lib/Transforms/Scalar/ScalarReplAggregates.cpp
index 53436000e03..c245b143273 100644
--- a/lib/Transforms/Scalar/ScalarReplAggregates.cpp
+++ b/lib/Transforms/Scalar/ScalarReplAggregates.cpp
@@ -193,6 +193,22 @@ private:
 };
 } // end anonymous namespace.
 
+
+/// IsVerbotenVectorType - Return true if this is a vector type ScalarRepl isn't
+/// allowed to form.  We do this to avoid MMX types, which is a complete hack,
+/// but is required until the backend is fixed.
+static bool IsVerbotenVectorType(const VectorType *VTy) {
+  // Reject all the MMX vector types.
+  switch (VTy->getNumElements()) {
+  default: return false;
+  case 1: return VTy->getElementType()->isIntegerTy(64);
+  case 2: return VTy->getElementType()->isIntegerTy(32);
+  case 4: return VTy->getElementType()->isIntegerTy(16);
+  case 8: return VTy->getElementType()->isIntegerTy(8);
+  }
+}
+
+
 /// TryConvert - Analyze the specified alloca, and if it is safe to do so,
 /// rewrite it to be a new alloca which is mem2reg'able.  This returns the new
 /// alloca if possible or null if not.
@@ -209,7 +225,8 @@ AllocaInst *ConvertToScalarInfo::TryConvert(AllocaInst *AI) {
   // we just get a lot of insert/extracts.  If at least one vector is
   // involved, then we probably really do have a union of vector/array.
   const Type *NewTy;
-  if (VectorTy && VectorTy->isVectorTy() && HadAVector) {
+  if (VectorTy && VectorTy->isVectorTy() && HadAVector &&
+      !IsVerbotenVectorType(cast<VectorType>(VectorTy))) {
     DEBUG(dbgs() << "CONVERT TO VECTOR: " << *AI << "\n  TYPE = "
           << *VectorTy << '\n');
     NewTy = VectorTy;  // Use the vector type.
@@ -1662,6 +1679,12 @@ void SROA::RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI,
 /// HasPadding - Return true if the specified type has any structure or
 /// alignment padding, false otherwise.
 static bool HasPadding(const Type *Ty, const TargetData &TD) {
+  if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty))
+    return HasPadding(ATy->getElementType(), TD);
+  
+  if (const VectorType *VTy = dyn_cast<VectorType>(Ty))
+    return HasPadding(VTy->getElementType(), TD);
+  
   if (const StructType *STy = dyn_cast<StructType>(Ty)) {
     const StructLayout *SL = TD.getStructLayout(STy);
     unsigned PrevFieldBitOffset = 0;
@@ -1691,12 +1714,8 @@ static bool HasPadding(const Type *Ty, const TargetData &TD) {
       if (PrevFieldEnd < SL->getSizeInBits())
         return true;
     }
-
-  } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
-    return HasPadding(ATy->getElementType(), TD);
-  } else if (const VectorType *VTy = dyn_cast<VectorType>(Ty)) {
-    return HasPadding(VTy->getElementType(), TD);
   }
+  
   return TD.getTypeSizeInBits(Ty) != TD.getTypeAllocSizeInBits(Ty);
 }
 
diff --git a/test/Transforms/ScalarRepl/vector_promote.ll b/test/Transforms/ScalarRepl/vector_promote.ll
index dd4251bde98..5287cbe38bf 100644
--- a/test/Transforms/ScalarRepl/vector_promote.ll
+++ b/test/Transforms/ScalarRepl/vector_promote.ll
@@ -85,3 +85,17 @@ define i32 @test5(float %X) {  ;; should turn into bitcast.
 ; CHECK-NEXT: ret i32
 }
 
+
+;; should not turn into <1 x i64> - It is a banned MMX datatype.
+;; rdar://8380055
+define i64 @test6(<2 x float> %X) {
+	%X_addr = alloca <2 x float>
+        store <2 x float> %X, <2 x float>* %X_addr
+	%P = bitcast <2 x float>* %X_addr to i64*
+	%tmp = load i64* %P
+	ret i64 %tmp
+; CHECK: @test6
+; CHECK-NEXT: bitcast <2 x float> %X to i64
+; CHECK-NEXT: ret i64
+}
+