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Commitfe2a16d

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llvmjit: Work around bug in LLVM 3.9 causing crashes after7255943.
Unfortunately in LLVM 3.9 LLVMGetAttributeCountAtIndex(func, index)crashes when called with an index that has 0 attributes. Since there'sno way to work around this in the C API, add a small C++ wrapper doingso.The only reason this didn't fail before7255943 is that therealways are function attributes...Author: Andres Freund <andres@anarazel.de>Discussion:https://postgr.es/m/20201016001254.w2nfj7gd74jmb5in@alap3.anarazel.deBackpatch: 11-, like7255943
1 parent536de14 commitfe2a16d

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3 files changed

+42
-1
lines changed

3 files changed

+42
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lines changed

‎src/backend/jit/llvm/llvmjit.c

Lines changed: 8 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -333,7 +333,14 @@ llvm_copy_attributes_at_index(LLVMValueRef v_from, LLVMValueRef v_to, uint32 ind
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intnum_attributes;
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LLVMAttributeRef*attrs;
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num_attributes=LLVMGetAttributeCountAtIndex(v_from,index);
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num_attributes=LLVMGetAttributeCountAtIndexPG(v_from,index);
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/*
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* Not just for efficiency: LLVM <= 3.9 crashes when
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* LLVMGetAttributesAtIndex() is called for an index with 0 attributes.
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*/
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if (num_attributes==0)
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return;
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attrs=palloc(sizeof(LLVMAttributeRef)*num_attributes);
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LLVMGetAttributesAtIndex(v_from,index,attrs);

‎src/backend/jit/llvm/llvmjit_wrap.cpp

Lines changed: 32 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -16,6 +16,13 @@ extern "C"
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#include"postgres.h"
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}
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#include<llvm-c/Core.h>
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/* Avoid macro clash with LLVM's C++ headers*/
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#undef Min
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#include<llvm/IR/Attributes.h>
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#include<llvm/IR/Function.h>
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#include<llvm/MC/SubtargetFeature.h>
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#include<llvm/Support/Host.h>
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@@ -44,3 +51,28 @@ char *LLVMGetHostCPUFeatures(void) {
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returnstrdup(Features.getString().c_str());
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}
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#endif
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/*
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* Like LLVM's LLVMGetAttributeCountAtIndex(), works around a bug in LLVM 3.9.
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*
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* In LLVM <= 3.9, LLVMGetAttributeCountAtIndex() segfaults if there are no
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* attributes at an index (fixed in LLVM commit ce9bb1097dc2).
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*/
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unsigned
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LLVMGetAttributeCountAtIndexPG(LLVMValueRef F, uint32 Idx)
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{
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/*
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* This is more expensive, so only do when using a problematic LLVM
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* version.
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*/
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#if LLVM_VERSION_MAJOR < 4
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if (!llvm::unwrap<llvm::Function>(F)->getAttributes().hasAttributes(Idx))
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return0;
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#endif
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/*
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* There is no nice public API to determine the count nicely, so just
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* always fall back to LLVM's C API.
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*/
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returnLLVMGetAttributeCountAtIndex(F, Idx);
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}

‎src/include/jit/llvmjit.h

Lines changed: 2 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -129,6 +129,8 @@ extern char *LLVMGetHostCPUName(void);
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externchar*LLVMGetHostCPUFeatures(void);
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#endif
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externunsignedLLVMGetAttributeCountAtIndexPG(LLVMValueRefF,uint32Idx);
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#ifdef__cplusplus
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}/* extern "C" */
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#endif

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