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.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@109854 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index 12185a3d4c38c7a107694335c52eeafd22458e8b..908a9d8919ddb0fd79e9cdd711d10bb7606f4117 100644 (file)
--- a/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -1968,12 +1968,9 @@ TargetLowering::SimplifySetCC(EVT VT, SDValue N0, SDValue N1,
       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;

diff --git a/test/CodeGen/X86/2010-07-29-SetccSimplify.ll b/test/CodeGen/X86/2010-07-29-SetccSimplify.ll
new file mode 100644 (file)
index 0000000..96016cf
--- /dev/null
+++ b/test/CodeGen/X86/2010-07-29-SetccSimplify.ll
@@ -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