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PR9055: extend the fix to PR4050 (r70179) to apply to zext and anyext.

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Returning a new node makes the code try to replace the old node, which
in the included testcase is killed by CSE.

llvm-svn: 129650
This commit is contained in:
Eli Friedman 2011-04-16 23:25:34 +00:00
parent 09c24968b1
commit 2798137293
2 changed files with 25 additions and 2 deletions
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4
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -3884,7 +3884,7 @@ SDValue DAGCombiner::visitZERO_EXTEND(SDNode *N) {
// CombineTo deleted the truncate, if needed, but not what's under it.
AddToWorkList(oye);
}
return DAG.getNode(ISD::ZERO_EXTEND, N->getDebugLoc(), VT, NarrowLoad);
return SDValue(N, 0); // Return N so it doesn't get rechecked!
}
}
@ -4112,7 +4112,7 @@ SDValue DAGCombiner::visitANY_EXTEND(SDNode *N) {
// CombineTo deleted the truncate, if needed, but not what's under it.
AddToWorkList(oye);
}
return DAG.getNode(ISD::ANY_EXTEND, N->getDebugLoc(), VT, NarrowLoad);
return SDValue(N, 0); // Return N so it doesn't get rechecked!
}
}

23
test/CodeGen/X86/fold-zext-trunc.ll Normal file
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@ -0,0 +1,23 @@
; RUN: llc < %s | FileCheck %s
; PR9055
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-f80:32:32-n8:16:32"
target triple = "i686-pc-linux-gnu"
%struct.S0 = type { i32, [2 x i8], [2 x i8], [4 x i8] }
@g_98 = common global %struct.S0 zeroinitializer, align 4
define void @foo() nounwind {
; CHECK: movzbl
; CHECK-NOT: movzbl
; CHECK: calll
entry:
%tmp17 = load i8* getelementptr inbounds (%struct.S0* @g_98, i32 0, i32 1, i32 0), align 4
%tmp54 = zext i8 %tmp17 to i32
%foo = load i32* bitcast (i8* getelementptr inbounds (%struct.S0* @g_98, i32 0, i32 1, i32 0) to i32*), align 4
%conv.i = trunc i32 %foo to i8
tail call void @func_12(i32 %tmp54, i8 zeroext %conv.i) nounwind
ret void
}
declare void @func_12(i32, i8 zeroext)