[llvm] [X86] Fold AND(Y, XOR(X, SUB(0, X))) to ANDN(Y, BLSMSK(X)) (PR #128348)
via llvm-commits
llvm-commits at lists.llvm.org
Sat Feb 22 00:57:05 PST 2025
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-backend-x86
Author: Marius Kamp (mskamp)
<details>
<summary>Changes</summary>
XOR(X, SUB(0, X)) corresponds to a bitwise-negated BLSMSK instruction
(i.e., x ^ (x - 1)). On its own, this transformation is probably not
really profitable but when the XOR operation is an operand of an AND
operation, we can use an ANDN instruction to reduce the number of
emitted instructions by one.
Fixes #<!-- -->103501.
---
Full diff: https://github.com/llvm/llvm-project/pull/128348.diff
2 Files Affected:
- (modified) llvm/lib/Target/X86/X86ISelLowering.cpp (+40)
- (added) llvm/test/CodeGen/X86/andnot-blsmsk.ll (+346)
``````````diff
diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 1c9d43ce4c062..81072f3a8995e 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -51045,6 +51045,41 @@ static SDValue combineBMILogicOp(SDNode *N, SelectionDAG &DAG,
return SDValue();
}
+/// Fold AND(Y, XOR(X, NEG(X))) -> ANDN(Y, BLSMSK(X)) if BMI is available.
+static SDValue combineAndXorSubWithBMI(SDValue Op, SDValue OtherOp, SDLoc DL,
+ SelectionDAG &DAG,
+ const X86Subtarget &Subtarget) {
+ EVT VT = Op.getValueType();
+ // Make sure this node is a candidate for BMI instructions.
+ if (!Subtarget.hasBMI() || !VT.isScalarInteger() ||
+ (VT != MVT::i32 && VT != MVT::i64))
+ return SDValue();
+
+ if (Op.getOpcode() != ISD::XOR || !Op.hasOneUse())
+ return SDValue();
+
+ // Make sure that the XOR operation corresponds to a negated BLSMSK
+ // instruction.
+ SDValue X = Op.getOperand(0);
+ SDValue Sub = Op.getOperand(1);
+ auto CheckOps = [&] {
+ return Sub.getOpcode() == ISD::SUB && Sub->hasOneUse() &&
+ isNullConstant(Sub.getOperand(0)) && Sub.getOperand(1) == X;
+ };
+ if (!CheckOps()) {
+ std::swap(X, Sub);
+ if (!CheckOps())
+ return SDValue();
+ }
+
+ SDValue BLSMSK =
+ DAG.getNode(ISD::XOR, DL, VT, X,
+ DAG.getNode(ISD::SUB, DL, VT, X, DAG.getConstant(1, DL, VT)));
+ SDValue AndN = DAG.getNode(ISD::AND, SDLoc(Op), VT, OtherOp,
+ DAG.getNOT(SDLoc(Op), BLSMSK, VT));
+ return AndN;
+}
+
static SDValue combineX86SubCmpForFlags(SDNode *N, SDValue Flag,
SelectionDAG &DAG,
TargetLowering::DAGCombinerInfo &DCI,
@@ -51453,6 +51488,11 @@ static SDValue combineAnd(SDNode *N, SelectionDAG &DAG,
if (SDValue R = combineBMILogicOp(N, DAG, Subtarget))
return R;
+ if (SDValue R = combineAndXorSubWithBMI(N0, N1, dl, DAG, Subtarget))
+ return R;
+ if (SDValue R = combineAndXorSubWithBMI(N1, N0, dl, DAG, Subtarget))
+ return R;
+
return SDValue();
}
diff --git a/llvm/test/CodeGen/X86/andnot-blsmsk.ll b/llvm/test/CodeGen/X86/andnot-blsmsk.ll
new file mode 100644
index 0000000000000..1e31ee075bfee
--- /dev/null
+++ b/llvm/test/CodeGen/X86/andnot-blsmsk.ll
@@ -0,0 +1,346 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
+; RUN: llc < %s -mtriple=i686-- -mattr=-bmi,+sse2 | FileCheck %s --check-prefixes=X86,X86-NOBMI
+; RUN: llc < %s -mtriple=i686-- -mattr=+bmi,+sse2 | FileCheck %s --check-prefixes=X86,X86-BMI
+; RUN: llc < %s -mtriple=x86_64-- -mattr=-bmi | FileCheck %s --check-prefixes=X64,X64-NOBMI
+; RUN: llc < %s -mtriple=x86_64-- -mattr=+bmi | FileCheck %s --check-prefixes=X64,X64-BMI
+
+declare void @use(i32)
+
+define i32 @fold_and_xor_neg_v1_32(i32 %x, i32 %y) {
+; X86-NOBMI-LABEL: fold_and_xor_neg_v1_32:
+; X86-NOBMI: # %bb.0:
+; X86-NOBMI-NEXT: movl {{[0-9]+}}(%esp), %ecx
+; X86-NOBMI-NEXT: movl %ecx, %eax
+; X86-NOBMI-NEXT: negl %eax
+; X86-NOBMI-NEXT: xorl %ecx, %eax
+; X86-NOBMI-NEXT: andl {{[0-9]+}}(%esp), %eax
+; X86-NOBMI-NEXT: retl
+;
+; X86-BMI-LABEL: fold_and_xor_neg_v1_32:
+; X86-BMI: # %bb.0:
+; X86-BMI-NEXT: blsmskl {{[0-9]+}}(%esp), %eax
+; X86-BMI-NEXT: andnl {{[0-9]+}}(%esp), %eax, %eax
+; X86-BMI-NEXT: retl
+;
+; X64-NOBMI-LABEL: fold_and_xor_neg_v1_32:
+; X64-NOBMI: # %bb.0:
+; X64-NOBMI-NEXT: movl %edi, %eax
+; X64-NOBMI-NEXT: negl %eax
+; X64-NOBMI-NEXT: xorl %edi, %eax
+; X64-NOBMI-NEXT: andl %esi, %eax
+; X64-NOBMI-NEXT: retq
+;
+; X64-BMI-LABEL: fold_and_xor_neg_v1_32:
+; X64-BMI: # %bb.0:
+; X64-BMI-NEXT: blsmskl %edi, %eax
+; X64-BMI-NEXT: andnl %esi, %eax, %eax
+; X64-BMI-NEXT: retq
+ %neg = sub i32 0, %x
+ %xor = xor i32 %x, %neg
+ %and = and i32 %xor, %y
+ ret i32 %and
+}
+
+define i32 @fold_and_xor_neg_v2_32(i32 %x, i32 %y) {
+; X86-NOBMI-LABEL: fold_and_xor_neg_v2_32:
+; X86-NOBMI: # %bb.0:
+; X86-NOBMI-NEXT: movl {{[0-9]+}}(%esp), %ecx
+; X86-NOBMI-NEXT: movl %ecx, %eax
+; X86-NOBMI-NEXT: negl %eax
+; X86-NOBMI-NEXT: xorl %ecx, %eax
+; X86-NOBMI-NEXT: andl {{[0-9]+}}(%esp), %eax
+; X86-NOBMI-NEXT: retl
+;
+; X86-BMI-LABEL: fold_and_xor_neg_v2_32:
+; X86-BMI: # %bb.0:
+; X86-BMI-NEXT: blsmskl {{[0-9]+}}(%esp), %eax
+; X86-BMI-NEXT: andnl {{[0-9]+}}(%esp), %eax, %eax
+; X86-BMI-NEXT: retl
+;
+; X64-NOBMI-LABEL: fold_and_xor_neg_v2_32:
+; X64-NOBMI: # %bb.0:
+; X64-NOBMI-NEXT: movl %edi, %eax
+; X64-NOBMI-NEXT: negl %eax
+; X64-NOBMI-NEXT: xorl %edi, %eax
+; X64-NOBMI-NEXT: andl %esi, %eax
+; X64-NOBMI-NEXT: retq
+;
+; X64-BMI-LABEL: fold_and_xor_neg_v2_32:
+; X64-BMI: # %bb.0:
+; X64-BMI-NEXT: blsmskl %edi, %eax
+; X64-BMI-NEXT: andnl %esi, %eax, %eax
+; X64-BMI-NEXT: retq
+ %neg = sub i32 0, %x
+ %xor = xor i32 %x, %neg
+ %and = and i32 %y, %xor
+ ret i32 %and
+}
+
+define i32 @fold_and_xor_neg_v3_32(i32 %x, i32 %y) {
+; X86-NOBMI-LABEL: fold_and_xor_neg_v3_32:
+; X86-NOBMI: # %bb.0:
+; X86-NOBMI-NEXT: movl {{[0-9]+}}(%esp), %ecx
+; X86-NOBMI-NEXT: movl %ecx, %eax
+; X86-NOBMI-NEXT: negl %eax
+; X86-NOBMI-NEXT: xorl %ecx, %eax
+; X86-NOBMI-NEXT: andl {{[0-9]+}}(%esp), %eax
+; X86-NOBMI-NEXT: retl
+;
+; X86-BMI-LABEL: fold_and_xor_neg_v3_32:
+; X86-BMI: # %bb.0:
+; X86-BMI-NEXT: blsmskl {{[0-9]+}}(%esp), %eax
+; X86-BMI-NEXT: andnl {{[0-9]+}}(%esp), %eax, %eax
+; X86-BMI-NEXT: retl
+;
+; X64-NOBMI-LABEL: fold_and_xor_neg_v3_32:
+; X64-NOBMI: # %bb.0:
+; X64-NOBMI-NEXT: movl %edi, %eax
+; X64-NOBMI-NEXT: negl %eax
+; X64-NOBMI-NEXT: xorl %edi, %eax
+; X64-NOBMI-NEXT: andl %esi, %eax
+; X64-NOBMI-NEXT: retq
+;
+; X64-BMI-LABEL: fold_and_xor_neg_v3_32:
+; X64-BMI: # %bb.0:
+; X64-BMI-NEXT: blsmskl %edi, %eax
+; X64-BMI-NEXT: andnl %esi, %eax, %eax
+; X64-BMI-NEXT: retq
+ %neg = sub i32 0, %x
+ %xor = xor i32 %neg, %x
+ %and = and i32 %xor, %y
+ ret i32 %and
+}
+
+define i32 @fold_and_xor_neg_v4_32(i32 %x, i32 %y) {
+; X86-NOBMI-LABEL: fold_and_xor_neg_v4_32:
+; X86-NOBMI: # %bb.0:
+; X86-NOBMI-NEXT: movl {{[0-9]+}}(%esp), %ecx
+; X86-NOBMI-NEXT: movl %ecx, %eax
+; X86-NOBMI-NEXT: negl %eax
+; X86-NOBMI-NEXT: xorl %ecx, %eax
+; X86-NOBMI-NEXT: andl {{[0-9]+}}(%esp), %eax
+; X86-NOBMI-NEXT: retl
+;
+; X86-BMI-LABEL: fold_and_xor_neg_v4_32:
+; X86-BMI: # %bb.0:
+; X86-BMI-NEXT: blsmskl {{[0-9]+}}(%esp), %eax
+; X86-BMI-NEXT: andnl {{[0-9]+}}(%esp), %eax, %eax
+; X86-BMI-NEXT: retl
+;
+; X64-NOBMI-LABEL: fold_and_xor_neg_v4_32:
+; X64-NOBMI: # %bb.0:
+; X64-NOBMI-NEXT: movl %edi, %eax
+; X64-NOBMI-NEXT: negl %eax
+; X64-NOBMI-NEXT: xorl %edi, %eax
+; X64-NOBMI-NEXT: andl %esi, %eax
+; X64-NOBMI-NEXT: retq
+;
+; X64-BMI-LABEL: fold_and_xor_neg_v4_32:
+; X64-BMI: # %bb.0:
+; X64-BMI-NEXT: blsmskl %edi, %eax
+; X64-BMI-NEXT: andnl %esi, %eax, %eax
+; X64-BMI-NEXT: retq
+ %neg = sub i32 0, %x
+ %xor = xor i32 %neg, %x
+ %and = and i32 %y, %xor
+ ret i32 %and
+}
+
+define i64 @fold_and_xor_neg_v1_64(i64 %x, i64 %y) {
+; X86-LABEL: fold_and_xor_neg_v1_64:
+; X86: # %bb.0:
+; X86-NEXT: pushl %esi
+; X86-NEXT: .cfi_def_cfa_offset 8
+; X86-NEXT: .cfi_offset %esi, -8
+; X86-NEXT: movl {{[0-9]+}}(%esp), %ecx
+; X86-NEXT: movl {{[0-9]+}}(%esp), %esi
+; X86-NEXT: xorl %edx, %edx
+; X86-NEXT: movl %ecx, %eax
+; X86-NEXT: negl %eax
+; X86-NEXT: sbbl %esi, %edx
+; X86-NEXT: xorl %esi, %edx
+; X86-NEXT: xorl %ecx, %eax
+; X86-NEXT: andl {{[0-9]+}}(%esp), %edx
+; X86-NEXT: andl {{[0-9]+}}(%esp), %eax
+; X86-NEXT: popl %esi
+; X86-NEXT: .cfi_def_cfa_offset 4
+; X86-NEXT: retl
+;
+; X64-NOBMI-LABEL: fold_and_xor_neg_v1_64:
+; X64-NOBMI: # %bb.0:
+; X64-NOBMI-NEXT: movq %rdi, %rax
+; X64-NOBMI-NEXT: negq %rax
+; X64-NOBMI-NEXT: xorq %rdi, %rax
+; X64-NOBMI-NEXT: andq %rsi, %rax
+; X64-NOBMI-NEXT: retq
+;
+; X64-BMI-LABEL: fold_and_xor_neg_v1_64:
+; X64-BMI: # %bb.0:
+; X64-BMI-NEXT: blsmskq %rdi, %rax
+; X64-BMI-NEXT: andnq %rsi, %rax, %rax
+; X64-BMI-NEXT: retq
+ %neg = sub i64 0, %x
+ %xor = xor i64 %x, %neg
+ %and = and i64 %xor, %y
+ ret i64 %and
+}
+
+; Negative test
+define i16 @fold_and_xor_neg_v1_16_negative(i16 %x, i16 %y) {
+; X86-LABEL: fold_and_xor_neg_v1_16_negative:
+; X86: # %bb.0:
+; X86-NEXT: movl {{[0-9]+}}(%esp), %ecx
+; X86-NEXT: movl %ecx, %eax
+; X86-NEXT: negl %eax
+; X86-NEXT: xorl %ecx, %eax
+; X86-NEXT: andw {{[0-9]+}}(%esp), %ax
+; X86-NEXT: # kill: def $ax killed $ax killed $eax
+; X86-NEXT: retl
+;
+; X64-LABEL: fold_and_xor_neg_v1_16_negative:
+; X64: # %bb.0:
+; X64-NEXT: movl %edi, %eax
+; X64-NEXT: negl %eax
+; X64-NEXT: xorl %edi, %eax
+; X64-NEXT: andl %esi, %eax
+; X64-NEXT: # kill: def $ax killed $ax killed $eax
+; X64-NEXT: retq
+ %neg = sub i16 0, %x
+ %xor = xor i16 %x, %neg
+ %and = and i16 %xor, %y
+ ret i16 %and
+}
+
+; Negative test
+define <4 x i32> @fold_and_xor_neg_v1_v4x32_negative(<4 x i32> %x, <4 x i32> %y) {
+; X86-LABEL: fold_and_xor_neg_v1_v4x32_negative:
+; X86: # %bb.0:
+; X86-NEXT: pxor %xmm2, %xmm2
+; X86-NEXT: psubd %xmm0, %xmm2
+; X86-NEXT: pxor %xmm2, %xmm0
+; X86-NEXT: pand %xmm1, %xmm0
+; X86-NEXT: retl
+;
+; X64-LABEL: fold_and_xor_neg_v1_v4x32_negative:
+; X64: # %bb.0:
+; X64-NEXT: pxor %xmm2, %xmm2
+; X64-NEXT: psubd %xmm0, %xmm2
+; X64-NEXT: pxor %xmm2, %xmm0
+; X64-NEXT: pand %xmm1, %xmm0
+; X64-NEXT: retq
+ %neg = sub <4 x i32> zeroinitializer, %x
+ %xor = xor <4 x i32> %x, %neg
+ %and = and <4 x i32> %xor, %y
+ ret <4 x i32> %and
+}
+
+; Negative test
+define i32 @fold_and_xor_neg_v1_32_two_uses_xor_negative(i32 %x, i32 %y) {
+; X86-LABEL: fold_and_xor_neg_v1_32_two_uses_xor_negative:
+; X86: # %bb.0:
+; X86-NEXT: pushl %esi
+; X86-NEXT: .cfi_def_cfa_offset 8
+; X86-NEXT: .cfi_offset %esi, -8
+; X86-NEXT: movl {{[0-9]+}}(%esp), %eax
+; X86-NEXT: movl %eax, %ecx
+; X86-NEXT: negl %ecx
+; X86-NEXT: xorl %eax, %ecx
+; X86-NEXT: movl {{[0-9]+}}(%esp), %esi
+; X86-NEXT: andl %ecx, %esi
+; X86-NEXT: pushl %ecx
+; X86-NEXT: .cfi_adjust_cfa_offset 4
+; X86-NEXT: calll use at PLT
+; X86-NEXT: addl $4, %esp
+; X86-NEXT: .cfi_adjust_cfa_offset -4
+; X86-NEXT: movl %esi, %eax
+; X86-NEXT: popl %esi
+; X86-NEXT: .cfi_def_cfa_offset 4
+; X86-NEXT: retl
+;
+; X64-LABEL: fold_and_xor_neg_v1_32_two_uses_xor_negative:
+; X64: # %bb.0:
+; X64-NEXT: pushq %rbx
+; X64-NEXT: .cfi_def_cfa_offset 16
+; X64-NEXT: .cfi_offset %rbx, -16
+; X64-NEXT: movl %esi, %ebx
+; X64-NEXT: movl %edi, %eax
+; X64-NEXT: negl %eax
+; X64-NEXT: xorl %eax, %edi
+; X64-NEXT: andl %edi, %ebx
+; X64-NEXT: callq use at PLT
+; X64-NEXT: movl %ebx, %eax
+; X64-NEXT: popq %rbx
+; X64-NEXT: .cfi_def_cfa_offset 8
+; X64-NEXT: retq
+ %neg = sub i32 0, %x
+ %xor = xor i32 %x, %neg
+ %and = and i32 %xor, %y
+ call void @use(i32 %xor)
+ ret i32 %and
+}
+
+; Negative test
+define i32 @fold_and_xor_neg_v1_32_two_uses_sub_negative(i32 %x, i32 %y) {
+; X86-LABEL: fold_and_xor_neg_v1_32_two_uses_sub_negative:
+; X86: # %bb.0:
+; X86-NEXT: pushl %esi
+; X86-NEXT: .cfi_def_cfa_offset 8
+; X86-NEXT: .cfi_offset %esi, -8
+; X86-NEXT: movl {{[0-9]+}}(%esp), %esi
+; X86-NEXT: movl %esi, %eax
+; X86-NEXT: negl %eax
+; X86-NEXT: xorl %eax, %esi
+; X86-NEXT: andl {{[0-9]+}}(%esp), %esi
+; X86-NEXT: pushl %eax
+; X86-NEXT: .cfi_adjust_cfa_offset 4
+; X86-NEXT: calll use at PLT
+; X86-NEXT: addl $4, %esp
+; X86-NEXT: .cfi_adjust_cfa_offset -4
+; X86-NEXT: movl %esi, %eax
+; X86-NEXT: popl %esi
+; X86-NEXT: .cfi_def_cfa_offset 4
+; X86-NEXT: retl
+;
+; X64-LABEL: fold_and_xor_neg_v1_32_two_uses_sub_negative:
+; X64: # %bb.0:
+; X64-NEXT: pushq %rbx
+; X64-NEXT: .cfi_def_cfa_offset 16
+; X64-NEXT: .cfi_offset %rbx, -16
+; X64-NEXT: movl %edi, %ebx
+; X64-NEXT: negl %edi
+; X64-NEXT: xorl %edi, %ebx
+; X64-NEXT: andl %esi, %ebx
+; X64-NEXT: callq use at PLT
+; X64-NEXT: movl %ebx, %eax
+; X64-NEXT: popq %rbx
+; X64-NEXT: .cfi_def_cfa_offset 8
+; X64-NEXT: retq
+ %neg = sub i32 0, %x
+ %xor = xor i32 %x, %neg
+ %and = and i32 %xor, %y
+ call void @use(i32 %neg)
+ ret i32 %and
+}
+
+; Negative test
+define i32 @fold_and_xor_neg_v1_32_no_blsmsk_negative(i32 %x, i32 %y, i32 %z) {
+; X86-LABEL: fold_and_xor_neg_v1_32_no_blsmsk_negative:
+; X86: # %bb.0:
+; X86-NEXT: xorl %eax, %eax
+; X86-NEXT: subl {{[0-9]+}}(%esp), %eax
+; X86-NEXT: xorl {{[0-9]+}}(%esp), %eax
+; X86-NEXT: andl {{[0-9]+}}(%esp), %eax
+; X86-NEXT: retl
+;
+; X64-LABEL: fold_and_xor_neg_v1_32_no_blsmsk_negative:
+; X64: # %bb.0:
+; X64-NEXT: movl %edx, %eax
+; X64-NEXT: negl %eax
+; X64-NEXT: xorl %edi, %eax
+; X64-NEXT: andl %esi, %eax
+; X64-NEXT: retq
+ %neg = sub i32 0, %z
+ %xor = xor i32 %x, %neg
+ %and = and i32 %xor, %y
+ ret i32 %and
+}
``````````
</details>
https://github.com/llvm/llvm-project/pull/128348
More information about the llvm-commits
mailing list