[PATCH] D53039: [sancov] Generalize the code to get the previous instruction to multiple architectures

[George Karpenkov via Phabricator via llvm-commits]

george.karpenkov created this revision.
george.karpenkov added reviewers: vsk, kubamracek, aizatsky, kcc.

sancov subtracts one from the address to get the previous instruction, which makes sense on x86_64, but not on other platforms.
This change ensures that the offset is correct for different platforms.
The logic for computing the offset is copied from sanitizer_common.


https://reviews.llvm.org/D53039

Files:
  llvm/tools/sancov/sancov.cpp


Index: llvm/tools/sancov/sancov.cpp
===================================================================
--- llvm/tools/sancov/sancov.cpp
+++ llvm/tools/sancov/sancov.cpp
@@ -766,6 +766,19 @@
   return Result;
 }
 
+static uint64_t getPreviousInstructionPc(uint64_t PC,
+                                         Triple TheTriple) {
+  if (TheTriple.isARM()) {
+    return (PC - 3) & (~1);
+  } else if (TheTriple.isAArch64()) {
+    return PC - 4;
+  } else if (TheTriple.isMIPS()) {
+    return PC - 8;
+  } else {
+    return PC - 1;
+  }
+}
+
 // Locate addresses of all coverage points in a file. Coverage point
 // is defined as the 'address of instruction following __sanitizer_cov
 // call - 1'.
@@ -832,7 +845,7 @@
       }
       uint64_t Addr = Index + SectionAddr;
       // Sanitizer coverage uses the address of the next instruction - 1.
-      uint64_t CovPoint = Addr + Size - 1;
+      uint64_t CovPoint = getPreviousInstructionPc(Addr + Size, TheTriple);
       uint64_t Target;
       if (MIA->isCall(Inst) &&
           MIA->evaluateBranch(Inst, SectionAddr + Index, Size, Target) &&


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