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When transforming sext(trunc(load(x))) into sext(smaller load(x)), 

the trunc is directly replaced with the smaller load, so don't
try to create a new sext node. This fixes PR4050.

llvm-svn: 70179
This commit is contained in:
Dan Gohman 2009-04-27 02:00:55 +00:00
parent 669e32f8c0
commit be36f5ccda
2 changed files with 21 additions and 1 deletions
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2
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
View File

@ -2962,7 +2962,7 @@ SDValue DAGCombiner::visitSIGN_EXTEND(SDNode *N) {
if (NarrowLoad.getNode()) {
if (NarrowLoad.getNode() != N0.getNode())
CombineTo(N0.getNode(), NarrowLoad);
return DAG.getNode(ISD::SIGN_EXTEND, N->getDebugLoc(), VT, NarrowLoad);
return SDValue(N, 0); // Return N so it doesn't get rechecked!
}
// See if the value being truncated is already sign extended. If so, just

20
llvm/test/CodeGen/X86/fold-sext-trunc.ll Normal file
View File

@ -0,0 +1,20 @@
; RUN: llvm-as < %s | llc -march=x86-64 | grep movslq | count 1
; PR4050
type { i64 } ; type %0
%struct.S1 = type { i16, i32 }
@g_10 = external global %struct.S1 ; <%struct.S1*> [#uses=2]
declare void @func_28(i64, i64)
define void @int322(i32 %foo) nounwind {
entry:
%val = load i64* getelementptr (%0* bitcast (%struct.S1* @g_10 to %0*), i32 0, i32 0) ; <i64> [#uses=1]
%0 = load i32* getelementptr (%struct.S1* @g_10, i32 0, i32 1), align 4 ; <i32> [#uses=1]
%1 = sext i32 %0 to i64 ; <i64> [#uses=1]
%tmp4.i = lshr i64 %val, 32 ; <i64> [#uses=1]
%tmp5.i = trunc i64 %tmp4.i to i32 ; <i32> [#uses=1]
%2 = sext i32 %tmp5.i to i64 ; <i64> [#uses=1]
tail call void @func_28(i64 %2, i64 %1) nounwind
ret void
}