[llvm] [AMDGPU] Search for literals among explicit operands only (PR #130771)

[Diana Picus via llvm-commits]

https://github.com/rovka created https://github.com/llvm/llvm-project/pull/130771

The code in SIInstrInfo::isOperandLegal crashes in some rare cases when dealing with call pseudos, which are variadic and may thus have more operands than those listed in their instruction descriptions. The excess operands will usually be implicit registers, but may also be the call preserved reg mask.

This patch attempts to fix the issue by iterating only through the explicit operands while searching for literal operands.

>From 0b1b82d52aa120a874655c9ee901dd4016de76e9 Mon Sep 17 00:00:00 2001
From: Diana Picus <diana-magda.picus at amd.com>
Date: Tue, 11 Mar 2025 13:33:38 +0100
Subject: [PATCH] [AMDGPU] Search for literals among explicit operands only

The code in SIInstrInfo::isOperandLegal crashes in some rare cases when
dealing with call pseudos, which are variadic and may thus have more
operands than those listed in their instruction descriptions. The excess
operands will usually be implicit registers, but may also be the call
preserved reg mask.

This patch attempts to fix the issue by iterating only through the
explicit operands while searching for literal operands.
---
 llvm/lib/Target/AMDGPU/SIInstrInfo.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/llvm/lib/Target/AMDGPU/SIInstrInfo.cpp b/llvm/lib/Target/AMDGPU/SIInstrInfo.cpp
index ae285d069d876..da8533fd5ef5d 100644
--- a/llvm/lib/Target/AMDGPU/SIInstrInfo.cpp
+++ b/llvm/lib/Target/AMDGPU/SIInstrInfo.cpp
@@ -6063,7 +6063,7 @@ bool SIInstrInfo::isOperandLegal(const MachineInstr &MI, unsigned OpIdx,
     }
   } else if (!IsInlineConst && !MO->isReg() && isSALU(MI)) {
     // There can be at most one literal operand, but it can be repeated.
-    for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
+    for (unsigned i = 0, e = MI.getNumExplicitOperands(); i != e; ++i) {
       if (i == OpIdx)
         continue;
       const MachineOperand &Op = MI.getOperand(i);