[llvm-commits] [llvm] r109854 - in /llvm/trunk: lib/CodeGen/SelectionDAG/TargetLowering.cpp test/CodeGen/X86/2010-07-29-SetccSimplify.ll

[Eli Friedman]

Author: efriedma
Date: Fri Jul 30 01:44:31 2010
New Revision: 109854

URL: http://llvm.org/viewvc/llvm-project?rev=109854&view=rev
Log:
Fix for bug reported by Evzen Muller on llvm-commits: make sure to correctly
check the range of the constant when optimizing a comparison between a
constant and a sign_extend_inreg node.


Added:
    llvm/trunk/test/CodeGen/X86/2010-07-29-SetccSimplify.ll
Modified:
    llvm/trunk/lib/CodeGen/SelectionDAG/TargetLowering.cpp

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/TargetLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/TargetLowering.cpp?rev=109854&r1=109853&r2=109854&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/TargetLowering.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/TargetLowering.cpp Fri Jul 30 01:44:31 2010
@@ -1968,12 +1968,9 @@
       EVT ExtDstTy = N0.getValueType();
       unsigned ExtDstTyBits = ExtDstTy.getSizeInBits();
 
-      // If the extended part has any inconsistent bits, it cannot ever
-      // compare equal.  In other words, they have to be all ones or all
-      // zeros.
-      APInt ExtBits =
-        APInt::getHighBitsSet(ExtDstTyBits, ExtDstTyBits - ExtSrcTyBits);
-      if ((C1 & ExtBits) != 0 && (C1 & ExtBits) != ExtBits)
+      // If the constant doesn't fit into the number of bits for the source of
+      // the sign extension, it is impossible for both sides to be equal.
+      if (C1.getMinSignedBits() > ExtSrcTyBits)
         return DAG.getConstant(Cond == ISD::SETNE, VT);
       
       SDValue ZextOp;

Added: llvm/trunk/test/CodeGen/X86/2010-07-29-SetccSimplify.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/2010-07-29-SetccSimplify.ll?rev=109854&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/X86/2010-07-29-SetccSimplify.ll (added)
+++ llvm/trunk/test/CodeGen/X86/2010-07-29-SetccSimplify.ll Fri Jul 30 01:44:31 2010
@@ -0,0 +1,14 @@
+; RUN: llc < %s -mtriple=x86_64-apple-darwin | FileCheck %s
+
+define i32 @extend2bit_v2(i32 %val) {
+entry:
+  %0 = trunc i32 %val to i2                       ; <i2> [#uses=1]
+  %1 = sext i2 %0 to i32                          ; <i32> [#uses=1]
+  %2 = icmp eq i32 %1, 3                          ; <i1> [#uses=1]
+  %3 = zext i1 %2 to i32                          ; <i32> [#uses=1]
+  ret i32 %3
+}
+
+; CHECK: extend2bit_v2:
+; CHECK: xorl	%eax, %eax
+; CHECK-NEXT: ret