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PR7814: Truncates cannot be ignored for signed comparisons.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@110268 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Eli Friedman 2010-08-04 22:40:58 +00:00
parent 59135f49e1
commit 7752442bfa
2 changed files with 38 additions and 1 deletions
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3
lib/Target/X86/X86ISelDAGToDAG.cpp
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@ -1841,7 +1841,8 @@ SDNode *X86DAGToDAGISel::Select(SDNode *Node) {
// Look for (X86cmp (and $op, $imm), 0) and see if we can convert it to
// use a smaller encoding.
if (N0.getOpcode() == ISD::TRUNCATE && N0.hasOneUse())
if (N0.getOpcode() == ISD::TRUNCATE && N0.hasOneUse() &&
HasNoSignedComparisonUses(Node))
// Look past the truncate if CMP is the only use of it.
N0 = N0.getOperand(0);
if (N0.getNode()->getOpcode() == ISD::AND && N0.getNode()->hasOneUse() &&

36
test/CodeGen/X86/2010-08-04-MaskedSignedCompare.ll Normal file
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@ -0,0 +1,36 @@
; RUN: llc < %s -march=x86-64 | FileCheck %s
; PR7814
@g_16 = global i64 -3738643449681751625, align 8 ; <i64*> [#uses=1]
@g_38 = global i32 0, align 4 ; <i32*> [#uses=2]
@.str = private constant [4 x i8] c"%d\0A\00" ; <[4 x i8]*> [#uses=1]
define i32 @main() nounwind {
entry:
%tmp = load i64* @g_16 ; <i64> [#uses=1]
%not.lnot = icmp ne i64 %tmp, 0 ; <i1> [#uses=1]
%conv = sext i1 %not.lnot to i64 ; <i64> [#uses=1]
%and = and i64 %conv, 150 ; <i64> [#uses=1]
%conv.i = trunc i64 %and to i8 ; <i8> [#uses=1]
%cmp = icmp sgt i8 %conv.i, 0 ; <i1> [#uses=1]
br i1 %cmp, label %if.then, label %entry.if.end_crit_edge
; CHECK: andl $150
; CHECK-NEXT: testb
; CHECK-NEXT: jg
entry.if.end_crit_edge: ; preds = %entry
%tmp4.pre = load i32* @g_38 ; <i32> [#uses=1]
br label %if.end
if.then: ; preds = %entry
store i32 1, i32* @g_38
br label %if.end
if.end: ; preds = %entry.if.end_crit_edge, %if.then
%tmp4 = phi i32 [ %tmp4.pre, %entry.if.end_crit_edge ], [ 1, %if.then ] ; <i32> [#uses=1]
%call5 = tail call i32 (i8*, ...)* @printf(i8* getelementptr inbounds ([4 x i8]* @.str, i64 0, i64 0), i32 %tmp4) nounwind ; <i32> [#uses=0]
ret i32 0
}
declare i32 @printf(i8* nocapture, ...) nounwind