Actually, disable this code for now. More analysis and improvements to

the X86 backend are needed before this should be enabled by default.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@44657 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 918db3835308261e051eb4d7dc6c4d90dd4750b7..ba3c0ac33dcb7f8773d928cc7a286ccbda404817 100644 (file)
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -2134,6 +2134,12 @@ SDOperand DAGCombiner::visitXOR(SDNode *N) {
 /// visitShiftByConstant - Handle transforms common to the three shifts, when
 /// the shift amount is a constant.
 SDOperand DAGCombiner::visitShiftByConstant(SDNode *N, unsigned Amt) {
+  // FIXME: disable this for now.  This pessimizes some common cases like:
+  //
+  //void foo(int *X, int i) { X[i & 1235] = 1; }
+  //int bar(int *X, int i) { return X[i & 255]; }
+  return SDOperand();
+  
   SDNode *LHS = N->getOperand(0).Val;
   if (!LHS->hasOneUse()) return SDOperand();
   

diff --git a/test/CodeGen/X86/shift-combine.ll b/test/CodeGen/X86/shift-combine.ll
index 543bb223787542e5fb702c1097975c479bca9b2b..c8df5b020800361b0b5d82a54a1832676aec7438 100644 (file)
--- a/test/CodeGen/X86/shift-combine.ll
+++ b/test/CodeGen/X86/shift-combine.ll
@@ -1,4 +1,5 @@
 ; RUN: llvm-as < %s | llc | not grep shrl
+; XFAIL: *
 
 target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
 target triple = "i686-apple-darwin8"