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Add a Win64 fast path for in-place small-block ReallocMem #98

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Add a Win64 fast path for in-place small-block ReallocMem #98

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25 changes: 24 additions & 1 deletion FastMM5.pas
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Original file line number Diff line number Diff line change
Expand Up @@ -8104,7 +8104,7 @@ function FastMM_ReallocMem(APointer: Pointer; ANewSize: NativeInt): Pointer;
mov eax, r8d
and eax, (CBlockIsFreeFlag or CIsSmallBlockFlag)
cmp eax, CIsSmallBlockFlag
je FastMM_ReallocMem_ReallocSmallBlock
je @SmallBlock

mov eax, r8d
and eax, (not CHasDebugInfoFlag)
Expand All @@ -8120,6 +8120,29 @@ function FastMM_ReallocMem(APointer: Pointer; ANewSize: NativeInt): Pointer;
xor edx,edx
jmp HandleInvalidFreeMemOrReallocMem

@SmallBlock:
{Inline the common in-place small-block downsize path. This avoids the compiler-generated frame and saved registers
in FastMM_ReallocMem_ReallocSmallBlock on Win64.}
mov r9d, r8d
and r9d, CDropSmallBlockFlagsMask
shl r9d, CSmallBlockSpanOffsetBitShift
mov rax, rcx
and rax, -CMediumBlockAlignment
sub rax, r9
mov rax, TSmallBlockSpanHeader(rax).SmallBlockManager
movzx r9d, TSmallBlockManager(rax).BlockSize
sub r9d, CSmallBlockHeaderSize

{Upsizes and large downsizes use the existing moving path.}
cmp r9, rdx
jb FastMM_ReallocMem_ReallocSmallBlock
lea r10, [rdx * 4 + CSmallBlockDownsizeCheckAdder]
cmp r10, r9
jb FastMM_ReallocMem_ReallocSmallBlock

mov rax, rcx
ret

{$endif}
{$else}
var
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