[AArch64][SelectionDAG] Mask for SUBS with multiple users cannot be elided #90911
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@llvm/pr-subscribers-backend-aarch64 Author: None (weihangf-apple) ChangesIn DAGCombiner, the Full diff: https://github.com/llvm/llvm-project/pull/90911.diff 2 Files Affected:
diff --git a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
index b27d204f3dded0..855573fdab9358 100644
--- a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -22833,7 +22833,8 @@ SDValue performCONDCombine(SDNode *N,
SDNode *SubsNode = N->getOperand(CmpIndex).getNode();
unsigned CondOpcode = SubsNode->getOpcode();
- if (CondOpcode != AArch64ISD::SUBS || SubsNode->hasAnyUseOfValue(0))
+ if (CondOpcode != AArch64ISD::SUBS || SubsNode->hasAnyUseOfValue(0) ||
+ !SubsNode->hasOneUse())
return SDValue();
// There is a SUBS feeding this condition. Is it fed by a mask we can
diff --git a/llvm/test/CodeGen/AArch64/and-mask-removal.ll b/llvm/test/CodeGen/AArch64/and-mask-removal.ll
index a8a59f1591268f..493d503de2cc13 100644
--- a/llvm/test/CodeGen/AArch64/and-mask-removal.ll
+++ b/llvm/test/CodeGen/AArch64/and-mask-removal.ll
@@ -526,4 +526,26 @@ define i64 @pr58109b(i8 signext %0, i64 %a, i64 %b) {
ret i64 %4
}
+define i64 @test_2_selects(i8 zeroext %a) {
+; CHECK-LABEL: test_2_selects:
+; CHECK: ; %bb.0:
+; CHECK-NEXT: add w9, w0, #24
+; CHECK-NEXT: mov w8, #131
+; CHECK-NEXT: and w9, w9, #0xff
+; CHECK-NEXT: cmp w9, #81
+; CHECK-NEXT: mov w9, #57
+; CHECK-NEXT: csel x8, x8, xzr, lo
+; CHECK-NEXT: csel x9, xzr, x9, eq
+; CHECK-NEXT: add x0, x8, x9
+; CHECK-NEXT: ret
+ %1 = add i8 %a, 24
+ %2 = zext i8 %1 to i64
+ %3 = icmp ult i8 %1, 81
+ %4 = select i1 %3, i64 131, i64 0
+ %5 = icmp eq i8 %1, 81
+ %6 = select i1 %5, i64 0, i64 57
+ %7 = add i64 %4, %6
+ ret i64 %7
+}
+
declare i8 @llvm.usub.sat.i8(i8, i8) #0
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@davemgreen Do you mind merging this PR for me since I don't have commit access? Thanks in advance! |
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@weihangf-apple Congratulations on having your first Pull Request (PR) merged into the LLVM Project! Your changes will be combined with recent changes from other authors, then tested Please check whether problems have been caused by your change specifically, as How to do this, and the rest of the post-merge process, is covered in detail here. If your change does cause a problem, it may be reverted, or you can revert it yourself. If you don't get any reports, no action is required from you. Your changes are working as expected, well done! |
…lided (llvm#90911) In DAGCombiner, the `performCONDCombine` function attempts to remove AND instructions in front of SUBS (cmp) instructions for which the AND is transparent. The rules for that are correct, but it fails to take into account the case where the SUBS instruction has multiple users with different condition codes for comparison and simply removes the AND for all of them. This causes a miscompilation in the attached test case. (cherry picked from commit 72eaa0e)
…lided (llvm#90911) In DAGCombiner, the `performCONDCombine` function attempts to remove AND instructions in front of SUBS (cmp) instructions for which the AND is transparent. The rules for that are correct, but it fails to take into account the case where the SUBS instruction has multiple users with different condition codes for comparison and simply removes the AND for all of them. This causes a miscompilation in the attached test case. (cherry picked from commit 72eaa0e)
…lided (llvm#90911) In DAGCombiner, the `performCONDCombine` function attempts to remove AND instructions in front of SUBS (cmp) instructions for which the AND is transparent. The rules for that are correct, but it fails to take into account the case where the SUBS instruction has multiple users with different condition codes for comparison and simply removes the AND for all of them. This causes a miscompilation in the attached test case. (cherry picked from commit 72eaa0e)
In DAGCombiner, the
performCONDCombinefunction attempts to remove AND instructions in front of SUBS (cmp) instructions for which the AND is transparent. The rules for that are correct, but it fails to take into account the case where the SUBS instruction has multiple users with different condition codes for comparison and simply removes the AND for all of them. This causes a miscompilation in the attached test case.