[llvm] b4e1466 - [AArch64] Improve codegen for shifted mask op
via llvm-commits
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Tue Nov 1 22:11:56 PDT 2022
Author: chenglin.bi
Date: 2022-11-02T13:11:48+08:00
New Revision: b4e1466c35d3ca3e04244e8e8b4ffaf0784d6d37
URL: https://github.com/llvm/llvm-project/commit/b4e1466c35d3ca3e04244e8e8b4ffaf0784d6d37
DIFF: https://github.com/llvm/llvm-project/commit/b4e1466c35d3ca3e04244e8e8b4ffaf0784d6d37.diff
LOG: [AArch64] Improve codegen for shifted mask op
The special case for bit extraction pattern is `((x >> C) & mask) << C`.
It can be combined to `x & (mask << C)` by return true in isDesirableToCommuteWithShift.
Fix: #56427
Reviewed By: dmgreen
Differential Revision: https://reviews.llvm.org/D136014
Added:
Modified:
llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
llvm/test/CodeGen/AArch64/shift-logic.ll
Removed:
################################################################################
diff --git a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
index 6571ddd7cb12b..17c489b2fb5ad 100644
--- a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -14442,15 +14442,23 @@ AArch64TargetLowering::isDesirableToCommuteWithShift(const SDNode *N,
SDValue ShiftLHS = N->getOperand(0);
EVT VT = N->getValueType(0);
- // If ShiftLHS is unsigned bit extraction: ((x >> C) & mask), then do not combine
- // it with shift 'N' to let it be lowered to UBFX.
+ // If ShiftLHS is unsigned bit extraction: ((x >> C) & mask), then do not
+ // combine it with shift 'N' to let it be lowered to UBFX except:
+ // ((x >> C) & mask) << C.
if (ShiftLHS.getOpcode() == ISD::AND && (VT == MVT::i32 || VT == MVT::i64) &&
isa<ConstantSDNode>(ShiftLHS.getOperand(1))) {
uint64_t TruncMask = ShiftLHS.getConstantOperandVal(1);
- if (isMask_64(TruncMask) &&
- ShiftLHS.getOperand(0).getOpcode() == ISD::SRL &&
- isa<ConstantSDNode>(ShiftLHS.getOperand(0).getOperand(1)))
- return false;
+ if (isMask_64(TruncMask)) {
+ SDValue AndLHS = ShiftLHS.getOperand(0);
+ if (AndLHS.getOpcode() == ISD::SRL) {
+ if (auto *SRLC = dyn_cast<ConstantSDNode>(AndLHS.getOperand(1))) {
+ if (N->getOpcode() == ISD::SHL)
+ if (auto *SHLC = dyn_cast<ConstantSDNode>(N->getOperand(1)))
+ return SRLC->getAPIntValue() == SHLC->getAPIntValue();
+ return false;
+ }
+ }
+ }
}
return true;
}
diff --git a/llvm/test/CodeGen/AArch64/shift-logic.ll b/llvm/test/CodeGen/AArch64/shift-logic.ll
index af684bbb8aff7..9a7cf004b3b74 100644
--- a/llvm/test/CodeGen/AArch64/shift-logic.ll
+++ b/llvm/test/CodeGen/AArch64/shift-logic.ll
@@ -151,3 +151,27 @@ define i32 @lshr_or_extra_use(i32 %x, i32 %y, i32* %p) nounwind {
%sh1 = lshr i32 %r, 7
ret i32 %sh1
}
+
+define i64 @desirable_to_commute1(i64 %x) {
+; CHECK-LABEL: desirable_to_commute1:
+; CHECK: // %bb.0:
+; CHECK-NEXT: and x0, x0, #0x7fff8
+; CHECK-NEXT: ret
+ %s1 = lshr i64 %x, 3
+ %a = and i64 %s1, 65535
+ %s2 = shl i64 %a, 3
+ ret i64 %s2
+}
+
+define i64 @desirable_to_commute2(i64* %p, i64 %i) {
+; CHECK-LABEL: desirable_to_commute2:
+; CHECK: // %bb.0:
+; CHECK-NEXT: and x8, x1, #0x1ff8
+; CHECK-NEXT: ldr x0, [x0, x8]
+; CHECK-NEXT: ret
+ %lshr = lshr i64 %i, 3
+ %and = and i64 %lshr, 1023
+ %pidx = getelementptr i64, i64* %p, i64 %and
+ %r = load i64, i64* %pidx
+ ret i64 %r
+}
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