https://github.com/tstellar updated
https://github.com/llvm/llvm-project/pull/86697
>From 647fbc710840d87698d9dbc016a90c3aa634f532 Mon Sep 17 00:00:00 2001
From: XChy <xxs_...@outlook.com>
Date: Fri, 22 Mar 2024 18:35:20 +0800
Subject: [PATCH] [SelectionDAG] Prevent combination on inconsistent type in
`combineCarryDiamond` (#84888)
Fixes #84831
When matching carry pattern with `getAsCarry`, it may produce different
type of carryout. This patch checks such case and does early exit.
I'm new to DAG, any suggestion is appreciated.
(cherry picked from commit cb4453dc69d75064c9a82e9a6a9bf0d0ded4b204)
---
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 7 +++++-
llvm/test/CodeGen/X86/addcarry.ll | 23 +++++++++++++++++++
2 files changed, 29 insertions(+), 1 deletion(-)
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 3135ec73a99e76..e806e0f0731f23 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -3575,6 +3575,11 @@ static SDValue combineCarryDiamond(SelectionDAG &DAG,
const TargetLowering &TLI,
return SDValue();
if (Opcode != ISD::UADDO && Opcode != ISD::USUBO)
return SDValue();
+ // Guarantee identical type of CarryOut
+ EVT CarryOutType = N->getValueType(0);
+ if (CarryOutType != Carry0.getValue(1).getValueType() ||
+ CarryOutType != Carry1.getValue(1).getValueType())
+ return SDValue();
// Canonicalize the add/sub of A and B (the top node in the above ASCII art)
// as Carry0 and the add/sub of the carry in as Carry1 (the middle node).
@@ -3622,7 +3627,7 @@ static SDValue combineCarryDiamond(SelectionDAG &DAG,
const TargetLowering &TLI,
// TODO: match other operations that can merge flags (ADD, etc)
DAG.ReplaceAllUsesOfValueWith(Carry1.getValue(0), Merged.getValue(0));
if (N->getOpcode() == ISD::AND)
- return DAG.getConstant(0, DL, MVT::i1);
+ return DAG.getConstant(0, DL, CarryOutType);
return Merged.getValue(1);
}
diff --git a/llvm/test/CodeGen/X86/addcarry.ll
b/llvm/test/CodeGen/X86/addcarry.ll
index 3fc4ed99fad0fa..f8d32fc2d29252 100644
--- a/llvm/test/CodeGen/X86/addcarry.ll
+++ b/llvm/test/CodeGen/X86/addcarry.ll
@@ -1490,3 +1490,26 @@ define { i64, i64 } @addcarry_commutative_2(i64 %x0, i64
%x1, i64 %y0, i64 %y1)
%r1 = insertvalue { i64, i64 } %r0, i64 %b1s, 1
ret { i64, i64 } %r1
}
+
+define i1 @pr84831(i64 %arg) {
+; CHECK-LABEL: pr84831:
+; CHECK: # %bb.0:
+; CHECK-NEXT: testq %rdi, %rdi
+; CHECK-NEXT: setne %al
+; CHECK-NEXT: xorl %ecx, %ecx
+; CHECK-NEXT: addb $-1, %al
+; CHECK-NEXT: adcq $1, %rcx
+; CHECK-NEXT: setb %al
+; CHECK-NEXT: retq
+ %a = icmp ult i64 0, %arg
+ %add1 = add i64 0, 1
+ %carryout1 = icmp ult i64 %add1, 0
+ %b = zext i1 %a to i64
+ %add2 = add i64 %add1, %b
+ %carryout2 = icmp ult i64 %add2, %add1
+ %zc1 = zext i1 %carryout1 to i63
+ %zc2 = zext i1 %carryout2 to i63
+ %or = or i63 %zc1, %zc2
+ %trunc = trunc i63 %or to i1
+ ret i1 %trunc
+}
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