[PATCH] D62828: [DAGCombiner][X86] Teach DAGCombiner to fold (not (neg X)) -> (add X, -1)
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Tue Jun 4 10:41:28 PDT 2019
This revision was automatically updated to reflect the committed changes.
Closed by commit rL362533: [DAGCombiner][X86] Fold (not (neg X)) -> (add X, -1) (authored by ctopper, committed by ).
Changed prior to commit:
https://reviews.llvm.org/D62828?vs=202810&id=202982#toc
Repository:
rL LLVM
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D62828/new/
https://reviews.llvm.org/D62828
Files:
llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
llvm/trunk/test/CodeGen/X86/bmi.ll
Index: llvm/trunk/test/CodeGen/X86/bmi.ll
===================================================================
--- llvm/trunk/test/CodeGen/X86/bmi.ll
+++ llvm/trunk/test/CodeGen/X86/bmi.ll
@@ -1153,10 +1153,7 @@
define void @pr42118_i32(i32 %x) {
; X86-LABEL: pr42118_i32:
; X86: # %bb.0:
-; X86-NEXT: movl {{[0-9]+}}(%esp), %eax
-; X86-NEXT: movl %eax, %ecx
-; X86-NEXT: negl %ecx
-; X86-NEXT: andnl %eax, %ecx, %eax
+; X86-NEXT: blsrl {{[0-9]+}}(%esp), %eax
; X86-NEXT: jne .LBB48_1
; X86-NEXT: # %bb.2:
; X86-NEXT: jmp bar # TAILCALL
@@ -1165,9 +1162,7 @@
;
; X64-LABEL: pr42118_i32:
; X64: # %bb.0:
-; X64-NEXT: movl %edi, %eax
-; X64-NEXT: negl %eax
-; X64-NEXT: andnl %edi, %eax, %eax
+; X64-NEXT: blsrl %edi, %eax
; X64-NEXT: jne .LBB48_1
; X64-NEXT: # %bb.2:
; X64-NEXT: jmp bar # TAILCALL
@@ -1192,13 +1187,13 @@
; X86-NEXT: .cfi_offset %esi, -8
; X86-NEXT: movl {{[0-9]+}}(%esp), %eax
; X86-NEXT: movl {{[0-9]+}}(%esp), %ecx
-; X86-NEXT: xorl %edx, %edx
-; X86-NEXT: movl %eax, %esi
-; X86-NEXT: negl %esi
-; X86-NEXT: sbbl %ecx, %edx
-; X86-NEXT: andnl %ecx, %edx, %ecx
-; X86-NEXT: andnl %eax, %esi, %eax
-; X86-NEXT: orl %ecx, %eax
+; X86-NEXT: movl %eax, %edx
+; X86-NEXT: addl $-1, %edx
+; X86-NEXT: movl %ecx, %esi
+; X86-NEXT: adcl $-1, %esi
+; X86-NEXT: andl %eax, %edx
+; X86-NEXT: andl %ecx, %esi
+; X86-NEXT: orl %edx, %esi
; X86-NEXT: jne .LBB49_1
; X86-NEXT: # %bb.2:
; X86-NEXT: popl %esi
@@ -1212,9 +1207,7 @@
;
; X64-LABEL: pr42118_i64:
; X64: # %bb.0:
-; X64-NEXT: movq %rdi, %rax
-; X64-NEXT: negq %rax
-; X64-NEXT: andnq %rdi, %rax, %rax
+; X64-NEXT: blsrq %rdi, %rax
; X64-NEXT: jne .LBB49_1
; X64-NEXT: # %bb.2:
; X64-NEXT: jmp bar # TAILCALL
Index: llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -6789,6 +6789,16 @@
return DAG.getNode(NewOpcode, DL, VT, LHS, RHS);
}
}
+
+ // fold (not (neg x)) -> (add X, -1)
+ // FIXME: This can be generalized to (not (sub Y, X)) -> (add X, ~Y) if
+ // Y is a constant or the subtract has a single use.
+ if (isAllOnesConstant(N1) && N0.getOpcode() == ISD::SUB &&
+ isNullConstant(N0.getOperand(0))) {
+ return DAG.getNode(ISD::ADD, DL, VT, N0.getOperand(1),
+ DAG.getAllOnesConstant(DL, VT));
+ }
+
// fold (xor (and x, y), y) -> (and (not x), y)
if (N0Opcode == ISD::AND && N0.hasOneUse() && N0->getOperand(1) == N1) {
SDValue X = N0.getOperand(0);
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