[llvm] b6ef408 - [JITLink][ELF] PCRel32GOTLoad edge offset can be smaller three

[Stefan Gränitz via llvm-commits]

Author: Stefan Gränitz
Date: 2020-10-24T16:57:48+02:00
New Revision: b6ef40891c7fb076a2f4ea860f8ee4135ae72aae

URL: https://github.com/llvm/llvm-project/commit/b6ef40891c7fb076a2f4ea860f8ee4135ae72aae
DIFF: https://github.com/llvm/llvm-project/commit/b6ef40891c7fb076a2f4ea860f8ee4135ae72aae.diff

LOG: [JITLink][ELF] PCRel32GOTLoad edge offset can be smaller three

Offset is 2 for MOVL instruction in test ELF_x86-64_common. This should fix the test failures.

Differential Revision: https://reviews.llvm.org/D89795

Added: 
    

Modified: 
    llvm/lib/ExecutionEngine/JITLink/ELF_x86_64.cpp

Removed: 
    


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diff  --git a/llvm/lib/ExecutionEngine/JITLink/ELF_x86_64.cpp b/llvm/lib/ExecutionEngine/JITLink/ELF_x86_64.cpp
index 821a7b3cc44e..fb931c3d85e9 100644
--- a/llvm/lib/ExecutionEngine/JITLink/ELF_x86_64.cpp
+++ b/llvm/lib/ExecutionEngine/JITLink/ELF_x86_64.cpp
@@ -127,12 +127,11 @@ static Error optimizeELF_x86_64_GOTAndStubs(LinkGraph &G) {
       if (E.getKind() == PCRel32GOTLoad) {
         // Replace GOT load with LEA only for MOVQ instructions.
         constexpr uint8_t MOVQRIPRel[] = {0x48, 0x8b};
-        if (strncmp(B->getContent().data() + E.getOffset() - 3,
+        if (E.getOffset() < 3 ||
+            strncmp(B->getContent().data() + E.getOffset() - 3,
                     reinterpret_cast<const char *>(MOVQRIPRel), 2) != 0)
           continue;
 
-        assert(E.getOffset() >= 3 && "GOT edge occurs too early in block");
-
         auto &GOTBlock = E.getTarget().getBlock();
         assert(GOTBlock.getSize() == G.getPointerSize() &&
                "GOT entry block should be pointer sized");