CodeGenPrep: sink extends of illegal types into use block.

Summary:
This helps the instruction selector to lower an i64 * i64 -> i128
multiplication into a single instruction on targets which support it.

This is an update of D2973 which was reverted because of a bug reported
as PR19084.

Reviewers: t.p.northover, chapuni

Reviewed By: t.p.northover

CC: llvm-commits, alex, chapuni

Differential Revision: http://llvm-reviews.chandlerc.com/D3021

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203797 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 49 insertions, 36 deletions

diff --git a/lib/CodeGen/CodeGenPrepare.cpp b/lib/CodeGen/CodeGenPrepare.cpp
index d53cdb97d9..428d8af359 100644
--- a/lib/CodeGen/CodeGenPrepare.cpp
+++ b/lib/CodeGen/CodeGenPrepare.cpp
@@ -464,40 +464,8 @@ void CodeGenPrepare::EliminateMostlyEmptyBlock(BasicBlock *BB) {
   DEBUG(dbgs() << "AFTER:\n" << *DestBB << "\n\n\n");
 }
 
-/// OptimizeNoopCopyExpression - If the specified cast instruction is a noop
-/// copy (e.g. it's casting from one pointer type to another, i32->i8 on PPC),
-/// sink it into user blocks to reduce the number of virtual
-/// registers that must be created and coalesced.
-///
-/// Return true if any changes are made.
-///
-static bool OptimizeNoopCopyExpression(CastInst *CI, const TargetLowering &TLI){
-  // If this is a noop copy,
-  EVT SrcVT = TLI.getValueType(CI->getOperand(0)->getType());
-  EVT DstVT = TLI.getValueType(CI->getType());
-
-  // This is an fp<->int conversion?
-  if (SrcVT.isInteger() != DstVT.isInteger())
-    return false;
-
-  // If this is an extension, it will be a zero or sign extension, which
-  // isn't a noop.
-  if (SrcVT.bitsLT(DstVT)) return false;
-
-  // If these values will be promoted, find out what they will be promoted
-  // to.  This helps us consider truncates on PPC as noop copies when they
-  // are.
-  if (TLI.getTypeAction(CI->getContext(), SrcVT) ==
-      TargetLowering::TypePromoteInteger)
-    SrcVT = TLI.getTypeToTransformTo(CI->getContext(), SrcVT);
-  if (TLI.getTypeAction(CI->getContext(), DstVT) ==
-      TargetLowering::TypePromoteInteger)
-    DstVT = TLI.getTypeToTransformTo(CI->getContext(), DstVT);
-
-  // If, after promotion, these are the same types, this is a noop copy.
-  if (SrcVT != DstVT)
-    return false;
-
+/// SinkCast - Sink the specified cast instruction into its user blocks
+static bool SinkCast(CastInst *CI) {
   BasicBlock *DefBB = CI->getParent();
 
   /// InsertedCasts - Only insert a cast in each block once.
@@ -547,6 +515,43 @@ static bool OptimizeNoopCopyExpression(CastInst *CI, const TargetLowering &TLI){
   return MadeChange;
 }
 
+/// OptimizeNoopCopyExpression - If the specified cast instruction is a noop
+/// copy (e.g. it's casting from one pointer type to another, i32->i8 on PPC),
+/// sink it into user blocks to reduce the number of virtual
+/// registers that must be created and coalesced.
+///
+/// Return true if any changes are made.
+///
+static bool OptimizeNoopCopyExpression(CastInst *CI, const TargetLowering &TLI){
+  // If this is a noop copy,
+  EVT SrcVT = TLI.getValueType(CI->getOperand(0)->getType());
+  EVT DstVT = TLI.getValueType(CI->getType());
+
+  // This is an fp<->int conversion?
+  if (SrcVT.isInteger() != DstVT.isInteger())
+    return false;
+
+  // If this is an extension, it will be a zero or sign extension, which
+  // isn't a noop.
+  if (SrcVT.bitsLT(DstVT)) return false;
+
+  // If these values will be promoted, find out what they will be promoted
+  // to.  This helps us consider truncates on PPC as noop copies when they
+  // are.
+  if (TLI.getTypeAction(CI->getContext(), SrcVT) ==
+      TargetLowering::TypePromoteInteger)
+    SrcVT = TLI.getTypeToTransformTo(CI->getContext(), SrcVT);
+  if (TLI.getTypeAction(CI->getContext(), DstVT) ==
+      TargetLowering::TypePromoteInteger)
+    DstVT = TLI.getTypeToTransformTo(CI->getContext(), DstVT);
+
+  // If, after promotion, these are the same types, this is a noop copy.
+  if (SrcVT != DstVT)
+    return false;
+
+  return SinkCast(CI);
+}
+
 /// OptimizeCmpExpression - sink the given CmpInst into user blocks to reduce
 /// the number of virtual registers that must be created and coalesced.  This is
 /// a clear win except on targets with multiple condition code registers
@@ -2811,8 +2816,16 @@ bool CodeGenPrepare::OptimizeInst(Instruction *I) {
       return true;
 
     if (isa<ZExtInst>(I) || isa<SExtInst>(I)) {
-      bool MadeChange = MoveExtToFormExtLoad(I);
-      return MadeChange | OptimizeExtUses(I);
+      /// Sink a zext or sext into its user blocks if the target type doesn't
+      /// fit in one register
+      if (TLI && TLI->getTypeAction(CI->getContext(),
+                                    TLI->getValueType(CI->getType())) ==
+                     TargetLowering::TypeExpandInteger) {
+        return SinkCast(CI);
+      } else {
+        bool MadeChange = MoveExtToFormExtLoad(I);
+        return MadeChange | OptimizeExtUses(I);
+      }
     }
     return false;
   }