Massive rewrite of MMX:

The x86_mmx type is used for MMX intrinsics, parameters and
return values where these use MMX registers, and is also
supported in load, store, and bitcast.

Only the above operations generate MMX instructions, and optimizations
do not operate on or produce MMX intrinsics. 

MMX-sized vectors <2 x i32> etc. are lowered to XMM or split into
smaller pieces.  Optimizations may occur on these forms and the
result casted back to x86_mmx, provided the result feeds into a
previous existing x86_mmx operation.

The point of all this is prevent optimizations from introducing
MMX operations, which is unsafe due to the EMMS problem.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@115243 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 14 insertions, 0 deletions

diff --git a/lib/VMCore/Instructions.cpp b/lib/VMCore/Instructions.cpp
index 7f8df58db5..754d992e6b 100644
--- a/lib/VMCore/Instructions.cpp
+++ b/lib/VMCore/Instructions.cpp
@@ -2360,6 +2360,8 @@ bool CastInst::isCastable(const Type *SrcTy, const Type *DestTy) {
     } else {                                    // Casting from something else
       return false;
     }
+  } else if (DestTy->isX86_MMXTy()) {     
+    return SrcBits == 64;
   } else {                                      // Casting to something else
     return false;
   }
@@ -2441,6 +2443,10 @@ CastInst::getCastOpcode(
       return BitCast;                             // vector -> vector
     } else if (DestPTy->getBitWidth() == SrcBits) {
       return BitCast;                               // float/int -> vector
+    } else if (SrcTy->isX86_MMXTy()) {
+      assert(DestPTy->getBitWidth()==64 &&
+             "Casting X86_MMX to vector of wrong width");
+      return BitCast;                             // MMX to 64-bit vector
     } else {
       assert(!"Illegal cast to vector (wrong type or size)");
     }
@@ -2452,6 +2458,14 @@ CastInst::getCastOpcode(
     } else {
       assert(!"Casting pointer to other than pointer or int");
     }
+  } else if (DestTy->isX86_MMXTy()) {
+    if (const VectorType *SrcPTy = dyn_cast<VectorType>(SrcTy)) {
+      assert(SrcPTy->getBitWidth()==64 &&
+             "Casting vector of wrong width to X86_MMX");
+      return BitCast;                               // 64-bit vector to MMX
+    } else {
+      assert(!"Illegal cast to X86_MMX");
+    }
   } else {
     assert(!"Casting to type that is not first-class");
   }