[clang] [llvm] [AMDGPU] Fix assertion failure isReg() in SIPreEmitPeephole (PR #176590)
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Sun Jan 18 02:37:14 PST 2026
https://github.com/Serosh-commits updated https://github.com/llvm/llvm-project/pull/176590
>From c01243bcbc79068bce0a3f7ad5a3779d53ea97c1 Mon Sep 17 00:00:00 2001
From: Serosh <janmejayapanda400 at gmail.com>
Date: Sat, 17 Jan 2026 16:46:46 +0530
Subject: [PATCH 1/3] [clang][bytecode] Fix stack corruption in pointer
arithmetic discard
In VisitPointerArithBinOp, the result of pointer addition or subtraction
was always left on the stack, even if the result was intended to be
discarded (e.g. in a comma expression). This led to stack corruption
where subsequent operations would find an unexpected pointer on the
stack, causing an assertion failure in the InterpStack.
This patch ensures that we correctly respect the DiscardResult flag
for pointer arithmetic operations.
Fixes #176549
---
clang/lib/AST/ByteCode/Compiler.cpp | 20 +++++++++++---------
clang/test/AST/ByteCode/gh176549.cpp | 8 ++++++++
2 files changed, 19 insertions(+), 9 deletions(-)
create mode 100644 clang/test/AST/ByteCode/gh176549.cpp
diff --git a/clang/lib/AST/ByteCode/Compiler.cpp b/clang/lib/AST/ByteCode/Compiler.cpp
index 21f8db06919ed..66b0cc4b5f6ab 100644
--- a/clang/lib/AST/ByteCode/Compiler.cpp
+++ b/clang/lib/AST/ByteCode/Compiler.cpp
@@ -1083,20 +1083,22 @@ bool Compiler<Emitter>::VisitPointerArithBinOp(const BinaryOperator *E) {
if (Op == BO_Add) {
if (!this->emitAddOffset(OffsetType, E))
return false;
-
- if (classifyPrim(E) != PT_Ptr)
- return this->emitDecayPtr(PT_Ptr, classifyPrim(E), E);
- return true;
- }
- if (Op == BO_Sub) {
+ } else if (Op == BO_Sub) {
if (!this->emitSubOffset(OffsetType, E))
return false;
+ } else {
+ return false;
+ }
- if (classifyPrim(E) != PT_Ptr)
- return this->emitDecayPtr(PT_Ptr, classifyPrim(E), E);
- return true;
+ if (classifyPrim(E) != PT_Ptr) {
+ if (!this->emitDecayPtr(PT_Ptr, classifyPrim(E), E))
+ return false;
}
+ if (DiscardResult)
+ return this->emitPop(classifyPrim(E), E);
+ return true;
+
return false;
}
diff --git a/clang/test/AST/ByteCode/gh176549.cpp b/clang/test/AST/ByteCode/gh176549.cpp
new file mode 100644
index 0000000000000..b56f762b7ede4
--- /dev/null
+++ b/clang/test/AST/ByteCode/gh176549.cpp
@@ -0,0 +1,8 @@
+// RUN: %clang_cc1 -fexperimental-new-constant-interpreter -verify %s
+// expected-no-diagnostics
+
+const char a[4] = "abc";
+void foo() {
+ int i = 0;
+ i = 1 > (a + 1, sizeof(a));
+}
>From 59f33d9ed24e822f84283fa84fd72e6b25b440d2 Mon Sep 17 00:00:00 2001
From: Serosh <janmejayapanda400 at gmail.com>
Date: Sun, 18 Jan 2026 00:34:45 +0530
Subject: [PATCH 2/3] [AMDGPU] Fix assertion failure in SIPreEmitPeephole
Fixes #176578. Add check for register operand before calling getReg() in optimizeVccBranch to prevent assertion failure when operand is an immediate.
---
llvm/lib/Target/AMDGPU/SIPreEmitPeephole.cpp | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/llvm/lib/Target/AMDGPU/SIPreEmitPeephole.cpp b/llvm/lib/Target/AMDGPU/SIPreEmitPeephole.cpp
index 8785968569d92..d15f89fdc78fc 100644
--- a/llvm/lib/Target/AMDGPU/SIPreEmitPeephole.cpp
+++ b/llvm/lib/Target/AMDGPU/SIPreEmitPeephole.cpp
@@ -153,11 +153,12 @@ bool SIPreEmitPeephole::optimizeVccBranch(MachineInstr &MI) const {
MachineOperand &Op1 = A->getOperand(1);
MachineOperand &Op2 = A->getOperand(2);
- if (Op1.getReg() != ExecReg && Op2.isReg() && Op2.getReg() == ExecReg) {
+ if ((!Op1.isReg() || Op1.getReg() != ExecReg) && Op2.isReg() &&
+ Op2.getReg() == ExecReg) {
TII->commuteInstruction(*A);
Changed = true;
}
- if (Op1.getReg() != ExecReg)
+ if (!Op1.isReg() || Op1.getReg() != ExecReg)
return Changed;
if (Op2.isImm() && !(Op2.getImm() == -1 || Op2.getImm() == 0))
return Changed;
>From 1b42936a2ee9b9a88279a4b718897167bfa14235 Mon Sep 17 00:00:00 2001
From: Serosh <janmejayapanda400 at gmail.com>
Date: Sun, 18 Jan 2026 00:35:08 +0530
Subject: [PATCH 3/3] [InstCombine] Fix compilation error in m_LogicalOp usages
Replace incorrect 3-argument m_LogicalOp matcher with explicit m_LogicalAnd/m_LogicalOr matchers.
---
.../InstCombine/InstCombineAndOrXor.cpp | 42 +++++++++++++++++++
1 file changed, 42 insertions(+)
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
index aacb2e2a91c57..80a7f0de363f0 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -3612,6 +3612,48 @@ Value *InstCombinerImpl::foldBooleanAndOr(Value *LHS, Value *RHS,
if (Value *Res = foldEqOfParts(LHS, RHS, IsAnd))
return Res;
+ // Handle reassociation-like folding: (A op B) op C --> A op (B op C)
+ // where B and C are ICmps and can be folded.
+ // This handles patterns like:
+ // select (and %cond, icmp1), icmp2, false -> select %cond, folded_icmp, false
+ // (A & icmp1) & icmp2 -> A & folded_icmp
+ auto TryFold = [&](Value *L, Value *R) -> Value * {
+ Value *A, *B;
+ Instruction::BinaryOps Opcode = IsAnd ? Instruction::And : Instruction::Or;
+
+ // Look through (Op A, B)
+ if (match(L, m_BinOp(Opcode, m_Value(A), m_Value(B))) ||
+ (IsLogical && (IsAnd ? match(L, m_LogicalAnd(m_Value(A), m_Value(B)))
+ : match(L, m_LogicalOr(m_Value(A), m_Value(B)))))) {
+ for (int i = 0; i < 2; ++i) {
+ Value *InnerCmp = i == 0 ? B : A;
+ Value *Other = i == 0 ? A : B;
+ auto *ICmpInner = dyn_cast<ICmpInst>(InnerCmp);
+ auto *ICmpR = dyn_cast<ICmpInst>(R);
+ if (ICmpInner && ICmpR) {
+ if (Value *Res = foldAndOrOfICmps(ICmpInner, ICmpR, I, IsAnd, IsLogical)) {
+ if (IsLogical) {
+ if (IsAnd)
+ return Builder.CreateSelect(Other, Res,
+ ConstantInt::getFalse(LHS->getType()));
+ else
+ return Builder.CreateSelect(Other, ConstantInt::getTrue(LHS->getType()),
+ Res);
+ } else {
+ return Builder.CreateBinOp(Opcode, Other, Res);
+ }
+ }
+ }
+ }
+ }
+ return nullptr;
+ };
+
+ if (Value *V = TryFold(LHS, RHS))
+ return V;
+ if (Value *V = TryFold(RHS, LHS))
+ return V;
+
return nullptr;
}
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