[llvm] 8a337c8 - Revert "[SPIR-V] Simplify and fix sign-extension bug in convertCharsToWord (#207769)" (#209162)

[via llvm-commits]

Author: Nikita Popov
Date: 2026-07-13T14:34:07+02:00
New Revision: 8a337c88d64e8d3fe918ae9fdc740fadbba2368c

URL: https://github.com/llvm/llvm-project/commit/8a337c88d64e8d3fe918ae9fdc740fadbba2368c
DIFF: https://github.com/llvm/llvm-project/commit/8a337c88d64e8d3fe918ae9fdc740fadbba2368c.diff

LOG: Revert "[SPIR-V] Simplify and fix sign-extension bug in convertCharsToWord (#207769)" (#209162)

This reverts commit 503f0ca19cfcc9c0c88d6918939a2c0038ad0498.

This is obviously incorrect on big endian architectures.

Added: 
    

Modified: 
    llvm/lib/Target/SPIRV/SPIRVUtils.cpp

Removed: 
    


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diff  --git a/llvm/lib/Target/SPIRV/SPIRVUtils.cpp b/llvm/lib/Target/SPIRV/SPIRVUtils.cpp
index 748783490ef64..c6f53609a2b3d 100644
--- a/llvm/lib/Target/SPIRV/SPIRVUtils.cpp
+++ b/llvm/lib/Target/SPIRV/SPIRVUtils.cpp
@@ -27,7 +27,6 @@
 #include "llvm/IR/IntrinsicInst.h"
 #include "llvm/IR/IntrinsicsSPIRV.h"
 #include "llvm/Support/MathExtras.h"
-#include <cstring>
 #include <queue>
 #include <vector>
 
@@ -147,9 +146,15 @@ StringRef getOriginalAsmConstraints(const CallBase &CB) {
 // when making string comparisons in compiler passes.
 // SPIR-V requires null-terminated UTF-8 strings padded to 32-bit alignment.
 static uint32_t convertCharsToWord(StringRef Str, unsigned i) {
-  uint32_t Word = 0u; // Padding/null bytes are zero-initialized.
-  unsigned Count = std::min(static_cast<size_t>(4), Str.size() - i);
-  std::memcpy(&Word, Str.data() + i, Count);
+  uint32_t Word = 0u; // Build up this 32-bit word from 4 8-bit chars.
+  for (unsigned WordIndex = 0; WordIndex < 4; ++WordIndex) {
+    unsigned StrIndex = i + WordIndex;
+    uint8_t CharToAdd = 0;       // Initilize char as padding/null.
+    if (StrIndex < Str.size()) { // If it's within the string, get a real char.
+      CharToAdd = Str[StrIndex];
+    }
+    Word |= (CharToAdd << (WordIndex * 8));
+  }
   return Word;
 }