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llvmjit: Work around bug in LLVM 3.9 causing crashes after 72559438f92.

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Unfortunately in LLVM 3.9 LLVMGetAttributeCountAtIndex(func, index)
crashes when called with an index that has 0 attributes. Since there's
no way to work around this in the C API, add a small C++ wrapper doing
so.

The only reason this didn't fail before 72559438f92 is that there
always are function attributes...

Author: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/20201016001254.w2nfj7gd74jmb5in@alap3.anarazel.de
Backpatch: 11-, like 72559438f92
This commit is contained in:
Andres Freund 2020-10-15 17:38:00 -07:00
parent 536de14e2b
commit fe2a16d8b3
3 changed files with 42 additions and 1 deletions
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9
src/backend/jit/llvm/llvmjit.c
View File

@ -333,7 +333,14 @@ llvm_copy_attributes_at_index(LLVMValueRef v_from, LLVMValueRef v_to, uint32 ind
int num_attributes;
LLVMAttributeRef *attrs;
num_attributes = LLVMGetAttributeCountAtIndex(v_from, index);
num_attributes = LLVMGetAttributeCountAtIndexPG(v_from, index);
/*
* Not just for efficiency: LLVM <= 3.9 crashes when
* LLVMGetAttributesAtIndex() is called for an index with 0 attributes.
*/
if (num_attributes == 0)
return;
attrs = palloc(sizeof(LLVMAttributeRef) * num_attributes);
LLVMGetAttributesAtIndex(v_from, index, attrs);

32
src/backend/jit/llvm/llvmjit_wrap.cpp
View File

@ -16,6 +16,13 @@ extern "C"
#include "postgres.h"
}
#include <llvm-c/Core.h>
/* Avoid macro clash with LLVM's C++ headers */
#undef Min
#include <llvm/IR/Attributes.h>
#include <llvm/IR/Function.h>
#include <llvm/MC/SubtargetFeature.h>
#include <llvm/Support/Host.h>
@ -44,3 +51,28 @@ char *LLVMGetHostCPUFeatures(void) {
return strdup(Features.getString().c_str());
}
#endif
/*
* Like LLVM's LLVMGetAttributeCountAtIndex(), works around a bug in LLVM 3.9.
*
* In LLVM <= 3.9, LLVMGetAttributeCountAtIndex() segfaults if there are no
* attributes at an index (fixed in LLVM commit ce9bb1097dc2).
*/
unsigned
LLVMGetAttributeCountAtIndexPG(LLVMValueRef F, uint32 Idx)
{
/*
* This is more expensive, so only do when using a problematic LLVM
* version.
*/
#if LLVM_VERSION_MAJOR < 4
if (!llvm::unwrap<llvm::Function>(F)->getAttributes().hasAttributes(Idx))
return 0;
#endif
/*
* There is no nice public API to determine the count nicely, so just
* always fall back to LLVM's C API.
*/
return LLVMGetAttributeCountAtIndex(F, Idx);
}

2
src/include/jit/llvmjit.h
View File

@ -129,6 +129,8 @@ extern char *LLVMGetHostCPUName(void);
extern char *LLVMGetHostCPUFeatures(void);
#endif
extern unsigned LLVMGetAttributeCountAtIndexPG(LLVMValueRef F, uint32 Idx);
#ifdef __cplusplus
} /* extern "C" */
#endif