Simplify hot-path size computations in BumpPtrAllocator. #101312
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@llvm/pr-subscribers-llvm-support Author: Owen Anderson (resistor) Changes~0.1% instruction count improvements Full diff: https://github.com/llvm/llvm-project/pull/101312.diff 1 Files Affected:
diff --git a/llvm/include/llvm/Support/Allocator.h b/llvm/include/llvm/Support/Allocator.h
index e05f0ec0e8704..d9a4f6599e6bb 100644
--- a/llvm/include/llvm/Support/Allocator.h
+++ b/llvm/include/llvm/Support/Allocator.h
@@ -149,8 +149,7 @@ class BumpPtrAllocatorImpl
// Keep track of how many bytes we've allocated.
BytesAllocated += Size;
- size_t Adjustment = offsetToAlignedAddr(CurPtr, Alignment);
- assert(Adjustment + Size >= Size && "Adjustment + Size must not overflow");
+ char* AlignedPtr = reinterpret_cast<char*>(alignAddr(CurPtr, Alignment));
size_t SizeToAllocate = Size;
#if LLVM_ADDRESS_SANITIZER_BUILD
@@ -158,12 +157,13 @@ class BumpPtrAllocatorImpl
SizeToAllocate += RedZoneSize;
#endif
+ char* AllocEndPtr = AlignedPtr + SizeToAllocate;
+
// Check if we have enough space.
- if (LLVM_LIKELY(Adjustment + SizeToAllocate <= size_t(End - CurPtr)
+ if (LLVM_LIKELY(AllocEndPtr <= End
// We can't return nullptr even for a zero-sized allocation!
&& CurPtr != nullptr)) {
- char *AlignedPtr = CurPtr + Adjustment;
- CurPtr = AlignedPtr + SizeToAllocate;
+ CurPtr = AllocEndPtr;
// Update the allocation point of this memory block in MemorySanitizer.
// Without this, MemorySanitizer messages for values originated from here
// will point to the allocation of the entire slab.
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✅ With the latest revision this PR passed the C/C++ code formatter. |
nikic
reviewed
Jul 31, 2024
| @@ -149,21 +149,21 @@ class BumpPtrAllocatorImpl | |||
| // Keep track of how many bytes we've allocated. | |||
| BytesAllocated += Size; | |||
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| size_t Adjustment = offsetToAlignedAddr(CurPtr, Alignment); | |||
| assert(Adjustment + Size >= Size && "Adjustment + Size must not overflow"); | |||
| char *AlignedPtr = reinterpret_cast<char *>(alignAddr(CurPtr, Alignment)); | |||
There was a problem hiding this comment.
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/171/builds/3403 Here is the relevant piece of the build log for the reference: |
resistor
added a commit
to resistor/llvm-project
that referenced
this pull request
Aug 1, 2024
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~0.1% instruction count improvements
https://llvm-compile-time-tracker.com/compare.php?from=07d2709a17860a202d91781769a88837e4fb5f2a&to=d5cc47831ecd9f0a2b164b16da67f74b94e9aafc&stat=instructions:u