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A new dag combine; several permutations of this

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are there under ADD, this one was missing.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@61107 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dale Johannesen 2008-12-16 22:13:49 +00:00
parent d0b6a0d967
commit fd3b7b7df3
2 changed files with 20 additions and 0 deletions
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6
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
View File

@ -1178,6 +1178,12 @@ SDValue DAGCombiner::visitSUB(SDNode *N) {
// fold (A+B)-B -> A
if (N0.getOpcode() == ISD::ADD && N0.getOperand(1) == N1)
return N0.getOperand(0);
// fold ((A+(B-C))-B) -> A-C
if (N0.getOpcode() == ISD::ADD &&
N0.getOperand(1).getOpcode() == ISD::SUB &&
N0.getOperand(1).getOperand(0) == N1)
return DAG.getNode(ISD::SUB, VT, N0.getOperand(0),
N0.getOperand(1).getOperand(1));
// 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/X86/2008-12-16-dagcombine-4.ll Normal file
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@ -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 %a, %L
%1 = add i32 %P, %0
%2 = sub i32 %1, %a
br label %return
return: ; preds = %bb3
ret i32 %2
}