[PATCH] D29528: [DAGCombiner] Push truncate through adde when the carry isn't used.
Amaury SECHET via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Fri Feb 3 18:26:45 PST 2017
deadalnix created this revision.
As per title.
https://reviews.llvm.org/D29528
Files:
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
test/CodeGen/X86/adde-carry.ll
Index: test/CodeGen/X86/adde-carry.ll
===================================================================
--- test/CodeGen/X86/adde-carry.ll
+++ test/CodeGen/X86/adde-carry.ll
@@ -105,9 +105,9 @@
; CHECK-NEXT: adcq $0, %rdx
; CHECK-NEXT: movq %rax, (%rdi)
; CHECK-NEXT: addq 8(%rdi), %rdx
-; CHECK-NEXT: sbbq %rax, %rax
-; CHECK-NEXT: andl $1, %eax
; CHECK-NEXT: movq %rdx, 8(%rdi)
+; CHECK-NEXT: sbbl %eax, %eax
+; CHECK-NEXT: andl $1, %eax
; CHECK-NEXT: addl %eax, 16(%rdi)
; CHECK-NEXT: retq
entry:
Index: lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -7778,6 +7778,7 @@
VT.getSizeInBits())))
return DAG.getNode(ISD::TRUNCATE, SDLoc(N), VT, Shorter);
}
+
// fold (truncate (load x)) -> (smaller load x)
// fold (truncate (srl (load x), c)) -> (smaller load (x+c/evtbits))
if (!LegalTypes || TLI.isTypeDesirableForOp(N0.getOpcode(), VT)) {
@@ -7864,6 +7865,18 @@
SimplifyDemandedBits(SDValue(N, 0)))
return SDValue(N, 0);
+ // (trunc adde(X, Y, Carry)) -> (adde trunc(X), trunc(Y), Carry)
+ // When the adde's carry is not used.
+ if (N0.getOpcode() == ISD::ADDE &&
+ N0.hasOneUse() &&
+ !N0.getNode()->hasAnyUseOfValue(1)) {
+ auto SL = SDLoc(N);
+ auto C1 = DAG.getNode(ISD::TRUNCATE, SL, VT, N0.getOperand(0));
+ auto C2 = DAG.getNode(ISD::TRUNCATE, SL, VT, N0.getOperand(1));
+ return DAG.getNode(ISD::ADDE, SL, DAG.getVTList(VT, MVT::Glue),
+ C1, C2, N0.getOperand(2));
+ }
+
return SDValue();
}
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