[clang] [clang][x86] Ensure we use the shifted value bit width to check for out of bounds per-element shift amounts (PR #156019)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Simon Pilgrim (RKSimon)

<details>
<summary>Changes</summary>

This should allow us to reuse these cases for the shift-by-immediate builtins in #<!-- -->155542

---
Full diff: https://github.com/llvm/llvm-project/pull/156019.diff


1 Files Affected:

- (modified) clang/lib/AST/ByteCode/InterpBuiltin.cpp (+6-6) 


``````````diff
diff --git a/clang/lib/AST/ByteCode/InterpBuiltin.cpp b/clang/lib/AST/ByteCode/InterpBuiltin.cpp
index eba0b25997699..3bfe54e00a049 100644
--- a/clang/lib/AST/ByteCode/InterpBuiltin.cpp
+++ b/clang/lib/AST/ByteCode/InterpBuiltin.cpp
@@ -3256,8 +3256,8 @@ bool InterpretBuiltin(InterpState &S, CodePtr OpPC, const CallExpr *Call,
   case clang::X86::BI__builtin_ia32_psllv8si:
     return interp__builtin_elementwise_int_binop(
         S, OpPC, Call, BuiltinID, [](const APSInt &LHS, const APSInt &RHS) {
-          if (RHS.uge(RHS.getBitWidth())) {
-            return APInt::getZero(RHS.getBitWidth());
+          if (RHS.uge(LHS.getBitWidth())) {
+            return APInt::getZero(LHS.getBitWidth());
           }
           return LHS.shl(RHS.getZExtValue());
         });
@@ -3266,8 +3266,8 @@ bool InterpretBuiltin(InterpState &S, CodePtr OpPC, const CallExpr *Call,
   case clang::X86::BI__builtin_ia32_psrav8si:
     return interp__builtin_elementwise_int_binop(
         S, OpPC, Call, BuiltinID, [](const APSInt &LHS, const APSInt &RHS) {
-          if (RHS.uge(RHS.getBitWidth())) {
-            return LHS.ashr(RHS.getBitWidth() - 1);
+          if (RHS.uge(LHS.getBitWidth())) {
+            return LHS.ashr(LHS.getBitWidth() - 1);
           }
           return LHS.ashr(RHS.getZExtValue());
         });
@@ -3278,8 +3278,8 @@ bool InterpretBuiltin(InterpState &S, CodePtr OpPC, const CallExpr *Call,
   case clang::X86::BI__builtin_ia32_psrlv8si:
     return interp__builtin_elementwise_int_binop(
         S, OpPC, Call, BuiltinID, [](const APSInt &LHS, const APSInt &RHS) {
-          if (RHS.uge(RHS.getBitWidth())) {
-            return APInt::getZero(RHS.getBitWidth());
+          if (RHS.uge(LHS.getBitWidth())) {
+            return APInt::getZero(LHS.getBitWidth());
           }
           return LHS.lshr(RHS.getZExtValue());
         });

``````````

</details>


https://github.com/llvm/llvm-project/pull/156019