From a787c9e23a4b30d3b93221ec93e7b5417f8a2235 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Sun, 28 Mar 2010 08:38:32 +0000
Subject: [PATCH] teach tblgen to allow patterns like (add (i32 (bitconvert
 (i32 GPR))), 4), transforming it into (add (i32 GPR), 4).  This allows us to
 write type generic multi patterns and have tblgen automatically drop the
 bitconvert in the case when the types align.  This allows us to fold an extra
 load in the changed testcase.

llvm-svn: 99756
---
 llvm/test/CodeGen/X86/2007-04-25-MMX-PADDQ.ll | 10 +++--
 llvm/utils/TableGen/CodeGenDAGPatterns.cpp    | 38 ++++++++++++++++++-
 2 files changed, 44 insertions(+), 4 deletions(-)

diff --git a/llvm/test/CodeGen/X86/2007-04-25-MMX-PADDQ.ll b/llvm/test/CodeGen/X86/2007-04-25-MMX-PADDQ.ll
index 113d0eb8647f..c39b82a1fe36 100644
--- a/llvm/test/CodeGen/X86/2007-04-25-MMX-PADDQ.ll
+++ b/llvm/test/CodeGen/X86/2007-04-25-MMX-PADDQ.ll
@@ -1,12 +1,16 @@
-; RUN: llc < %s -o - -march=x86 -mattr=+mmx | grep paddq | count 2
-; RUN: llc < %s -o - -march=x86 -mattr=+mmx | grep movq | count 2
+; RUN: llc < %s -o - -march=x86 -mattr=+mmx | FileCheck %s
 
-define <1 x i64> @unsigned_add3(<1 x i64>* %a, <1 x i64>* %b, i32 %count) {
+define <1 x i64> @unsigned_add3(<1 x i64>* %a, <1 x i64>* %b, i32 %count) nounwind {
 entry:
 	%tmp2942 = icmp eq i32 %count, 0		; <i1> [#uses=1]
 	br i1 %tmp2942, label %bb31, label %bb26
 
 bb26:		; preds = %bb26, %entry
+
+; CHECK:  movq	({{.*}},8), %mm
+; CHECK:  paddq	({{.*}},8), %mm
+; CHECK:  paddq	%mm{{[0-7]}}, %mm
+
 	%i.037.0 = phi i32 [ 0, %entry ], [ %tmp25, %bb26 ]		; <i32> [#uses=3]
 	%sum.035.0 = phi <1 x i64> [ zeroinitializer, %entry ], [ %tmp22, %bb26 ]		; <<1 x i64>> [#uses=1]
 	%tmp13 = getelementptr <1 x i64>* %b, i32 %i.037.0		; <<1 x i64>*> [#uses=1]
diff --git a/llvm/utils/TableGen/CodeGenDAGPatterns.cpp b/llvm/utils/TableGen/CodeGenDAGPatterns.cpp
index 6bb239ac69af..a29c5539fc84 100644
--- a/llvm/utils/TableGen/CodeGenDAGPatterns.cpp
+++ b/llvm/utils/TableGen/CodeGenDAGPatterns.cpp
@@ -1591,6 +1591,40 @@ TreePatternNode *TreePattern::ParseTreePattern(Init *TheInit, StringRef OpName){
   return Result;
 }
 
+/// SimplifyTree - See if we can simplify this tree to eliminate something that
+/// will never match in favor of something obvious that will.  This is here
+/// strictly as a convenience to target authors because it allows them to write
+/// more type generic things and have useless type casts fold away.
+///
+/// This returns true if any change is made.
+static bool SimplifyTree(TreePatternNode *&N) {
+  if (N->isLeaf())
+    return false;
+
+  // If we have a bitconvert with a resolved type and if the source and
+  // destination types are the same, then the bitconvert is useless, remove it.
+  if (N->getOperator()->getName() == "bitconvert" &&
+      N->getNumChildren() > 0 && // FIXME
+      N->getExtType(0).isConcrete() &&
+      N->getExtType(0) == N->getChild(0)->getExtType(0) &&
+      N->getName().empty()) {
+    N = N->getChild(0);
+    SimplifyTree(N);
+    return true;
+  }
+
+  // Walk all children.
+  bool MadeChange = false;
+  for (unsigned i = 0, e = N->getNumChildren(); i != e; ++i) {
+    TreePatternNode *Child = N->getChild(i);
+    MadeChange |= SimplifyTree(Child);
+    N->setChild(i, Child);
+  }
+  return MadeChange;
+}
+
+
+
 /// InferAllTypes - Infer/propagate as many types throughout the expression
 /// patterns as possible.  Return true if all types are inferred, false
 /// otherwise.  Throw an exception if a type contradiction is found.
@@ -1602,8 +1636,10 @@ InferAllTypes(const StringMap<SmallVector<TreePatternNode*,1> > *InNamedTypes) {
   bool MadeChange = true;
   while (MadeChange) {
     MadeChange = false;
-    for (unsigned i = 0, e = Trees.size(); i != e; ++i)
+    for (unsigned i = 0, e = Trees.size(); i != e; ++i) {
       MadeChange |= Trees[i]->ApplyTypeConstraints(*this, false);
+      MadeChange |= SimplifyTree(Trees[i]);
+    }
 
     // If there are constraints on our named nodes, apply them.
     for (StringMap<SmallVector<TreePatternNode*,1> >::iterator