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One more permutation of subtracting off a base value.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@61361 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dale Johannesen 2008-12-23 01:59:54 +00:00
parent ae53c932b9
commit 58e39b0200
2 changed files with 20 additions and 0 deletions
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6
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -1184,6 +1184,12 @@ SDValue DAGCombiner::visitSUB(SDNode *N) {
N0.getOperand(1).getOperand(0) == N1)
return DAG.getNode(ISD::SUB, VT, N0.getOperand(0),
N0.getOperand(1).getOperand(1));
// fold ((A-(B-C))-C) -> A-B
if (N0.getOpcode() == ISD::SUB &&
N0.getOperand(1).getOpcode() == ISD::SUB &&
N0.getOperand(1).getOperand(1) == N1)
return DAG.getNode(ISD::SUB, VT, N0.getOperand(0),
N0.getOperand(1).getOperand(0));
// fold (sub x, (select cc, 0, c)) -> (select cc, x, (sub, x, c))
if (N1.getOpcode() == ISD::SELECT && N1.getNode()->hasOneUse()) {
SDValue Result = combineSelectAndUse(N, N1, N0, DAG, TLI, LegalOperations);

14
test/CodeGen/X86/2008-12-22-dagcombine-5.ll Normal file
View File

@ -0,0 +1,14 @@
; RUN: llvm-as < %s | llc -march=x86 | grep "(%esp)" | count 2
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-f80:128:128"
target triple = "i386-apple-darwin9.5"
; -(-a) - a should be found and removed, leaving refs to only L and P
define i32 @test(i32 %a, i32 %L, i32 %P) nounwind {
entry:
%0 = sub i32 %L, %a
%1 = sub i32 %P, %0
%2 = sub i32 %1, %a
br label %return
return: ; preds = %bb3
ret i32 %2
}