GlobalISel: Guard return in llvm::getIConstantSplatVal

[changpeng]

getIConstantVRegValWithLookThrough could return NULL.

[llvmbot]

@llvm/pr-subscribers-backend-amdgpu

@llvm/pr-subscribers-llvm-globalisel

Author: Changpeng Fang (changpeng)

Changes

getIConstantVRegValWithLookThrough could return NULL.

---

Full diff: https://github.com/llvm/llvm-project/pull/71989.diff

1 Files Affected:

• (modified) llvm/lib/CodeGen/GlobalISel/Utils.cpp (+3-3)

diff --git a/llvm/lib/CodeGen/GlobalISel/Utils.cpp b/llvm/lib/CodeGen/GlobalISel/Utils.cpp
index 473c3f452f8b1d9..eaf829f562b2dc9 100644
--- a/llvm/lib/CodeGen/GlobalISel/Utils.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/Utils.cpp
@@ -1116,9 +1116,9 @@ std::optional<APInt>
 llvm::getIConstantSplatVal(const Register Reg, const MachineRegisterInfo &MRI) {
   if (auto SplatValAndReg =
           getAnyConstantSplat(Reg, MRI, /* AllowUndef */ false)) {
-    std::optional<ValueAndVReg> ValAndVReg =
-        getIConstantVRegValWithLookThrough(SplatValAndReg->VReg, MRI);
-    return ValAndVReg->Value;
+    if (std::optional<ValueAndVReg> ValAndVReg =
+        getIConstantVRegValWithLookThrough(SplatValAndReg->VReg, MRI))
+      return ValAndVReg->Value;
   }
 
   return std::nullopt;

[github-actions]

⚠️ C/C++ code formatter, clang-format found issues in your code. ⚠️

You can test this locally with the following command:

git-clang-format --diff d2fd1106f6879c410b6a807133090866e6c3a243 2155fe1374ead3bc4a1db6f4856ab1d0cf2392ff -- llvm/lib/CodeGen/GlobalISel/Utils.cpp

View the diff from clang-format here.

diff --git a/llvm/lib/CodeGen/GlobalISel/Utils.cpp b/llvm/lib/CodeGen/GlobalISel/Utils.cpp
index eaf829f562..e4a69a1600 100644
--- a/llvm/lib/CodeGen/GlobalISel/Utils.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/Utils.cpp
@@ -1117,7 +1117,7 @@ llvm::getIConstantSplatVal(const Register Reg, const MachineRegisterInfo &MRI) {
   if (auto SplatValAndReg =
           getAnyConstantSplat(Reg, MRI, /* AllowUndef */ false)) {
     if (std::optional<ValueAndVReg> ValAndVReg =
-        getIConstantVRegValWithLookThrough(SplatValAndReg->VReg, MRI))
+            getIConstantVRegValWithLookThrough(SplatValAndReg->VReg, MRI))
       return ValAndVReg->Value;
   }
 

[rampitec]

Any tests?

[changpeng]

Any tests?
Encountered this issue during a downstream branch testing. No test for trunk yet but think the issue should be here.

[jayfoad]

Typo in subject "Guard return ..."?

[changpeng]

Typo in subject "Guard return ..."?

You are right. Thanks.

[qcolombet]

@changpeng
A comment here would be nice.
E.g., "Even if the value is a splat constant, it may not be an integer one."