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When resolving a stub in x86-64 JIT, use a PC-relative branch

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rather than the absolute address if the target is within range.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@54708 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dale Johannesen 2008-08-12 23:20:24 +00:00
parent f9e67aca52
commit 6f83be0c61
1 changed files with 14 additions and 2 deletions
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16
lib/Target/X86/X86JITInfo.cpp
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@ -352,7 +352,8 @@ X86CompilationCallback2(intptr_t *StackPtr, intptr_t RetAddr) {
// Rewrite the call target... so that we don't end up here every time we
// execute the call.
#if defined (X86_64_JIT)
*(intptr_t *)(RetAddr - 0xa) = NewVal;
if (!isStub)
*(intptr_t *)(RetAddr - 0xa) = NewVal;
#else
*(intptr_t *)RetAddr = (intptr_t)(NewVal-RetAddr-4);
#endif
@ -363,7 +364,18 @@ X86CompilationCallback2(intptr_t *StackPtr, intptr_t RetAddr) {
// when the requested function finally gets called. This also makes the
// 0xCD byte (interrupt) dead, so the marker doesn't effect anything.
#if defined (X86_64_JIT)
((unsigned char*)RetAddr)[0] = (2 | (4 << 3) | (3 << 6));
// If the target address is within 32-bit range of the stub, use a
// PC-relative branch instead of loading the actual address. (This is
// considerably shorter than the 64-bit immediate load already there.)
// We assume here intptr_t is 64 bits.
intptr_t diff = NewVal-RetAddr+7;
if (diff >= -2147483648LL && diff <= 2147483647LL) {
*(unsigned char*)(RetAddr-0xc) = 0xE9;
*(intptr_t *)(RetAddr-0xb) = diff & 0xffffffff;
} else {
*(intptr_t *)(RetAddr - 0xa) = NewVal;
((unsigned char*)RetAddr)[0] = (2 | (4 << 3) | (3 << 6));
}
#else
((unsigned char*)RetAddr)[-1] = 0xE9;
#endif