[llvm] afa413a - [RemoveDIs][DebugInfo] Correctly visit DPValues in StackInfoBuilder::visit (#81247)

[via llvm-commits]

Author: Stephen Tozer
Date: 2024-02-12T13:50:37Z
New Revision: afa413a132c0959295df36c28814ee83948e4931

URL: https://github.com/llvm/llvm-project/commit/afa413a132c0959295df36c28814ee83948e4931
DIFF: https://github.com/llvm/llvm-project/commit/afa413a132c0959295df36c28814ee83948e4931.diff

LOG: [RemoveDIs][DebugInfo] Correctly visit DPValues in StackInfoBuilder::visit (#81247)

In `StackInfoBuilder::visit(Instruction &Inst)`, operations are
performed on memory-related instructions, including debug intrinsics
that refer to "interesting" allocas. There is a block that also visits
DPValues attached to the instruction, but this block is near the end of
the function; this has two problems:
1. The DPValues attached to an instruction precede that instruction, so
they should always be processed before the instruction itself.
2. More importantly, some of the paths for visiting other instructions
contain early returns, which will result in the DPValues not being
visited at all.

This patch simply moves the DPValue-visiting block to the top of the
function, which should resolve both of these problems.

Added: 
    

Modified: 
    llvm/lib/Transforms/Utils/MemoryTaggingSupport.cpp
    llvm/test/Instrumentation/HWAddressSanitizer/dbg-declare-tag-offset.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Utils/MemoryTaggingSupport.cpp b/llvm/lib/Transforms/Utils/MemoryTaggingSupport.cpp
index 648a5276a3d60a..43366950d8df1e 100644
--- a/llvm/lib/Transforms/Utils/MemoryTaggingSupport.cpp
+++ b/llvm/lib/Transforms/Utils/MemoryTaggingSupport.cpp
@@ -110,6 +110,20 @@ Instruction *getUntagLocationIfFunctionExit(Instruction &Inst) {
 }
 
 void StackInfoBuilder::visit(Instruction &Inst) {
+  // Check for non-intrinsic debug-info records.
+  for (auto &DPV : Inst.getDbgValueRange()) {
+    for (Value *V : DPV.location_ops()) {
+      if (auto *AI = dyn_cast_or_null<AllocaInst>(V)) {
+        if (!isInterestingAlloca(*AI))
+          continue;
+        AllocaInfo &AInfo = Info.AllocasToInstrument[AI];
+        auto &DPVVec = AInfo.DbgVariableRecords;
+        if (DPVVec.empty() || DPVVec.back() != &DPV)
+          DPVVec.push_back(&DPV);
+      }
+    }
+  }
+
   if (CallInst *CI = dyn_cast<CallInst>(&Inst)) {
     if (CI->canReturnTwice()) {
       Info.CallsReturnTwice = true;
@@ -150,20 +164,6 @@ void StackInfoBuilder::visit(Instruction &Inst) {
     }
   }
 
-  // Check for non-intrinsic debug-info records.
-  for (auto &DPV : Inst.getDbgValueRange()) {
-    for (Value *V : DPV.location_ops()) {
-      if (auto *AI = dyn_cast_or_null<AllocaInst>(V)) {
-        if (!isInterestingAlloca(*AI))
-          continue;
-        AllocaInfo &AInfo = Info.AllocasToInstrument[AI];
-        auto &DPVVec = AInfo.DbgVariableRecords;
-        if (DPVVec.empty() || DPVVec.back() != &DPV)
-          DPVVec.push_back(&DPV);
-      }
-    }
-  }
-
   Instruction *ExitUntag = getUntagLocationIfFunctionExit(Inst);
   if (ExitUntag)
     Info.RetVec.push_back(ExitUntag);

diff  --git a/llvm/test/Instrumentation/HWAddressSanitizer/dbg-declare-tag-offset.ll b/llvm/test/Instrumentation/HWAddressSanitizer/dbg-declare-tag-offset.ll
index d5e362bc800ad8..50bad19250267c 100644
--- a/llvm/test/Instrumentation/HWAddressSanitizer/dbg-declare-tag-offset.ll
+++ b/llvm/test/Instrumentation/HWAddressSanitizer/dbg-declare-tag-offset.ll
@@ -1,5 +1,10 @@
 ; RUN: opt -passes=hwasan -S -o - %s | FileCheck %s
 
+;; Also test with RemoveDIs to verify that debug intrinsics immediately
+;; preceding an alloca (or other instruction of interest to stack tagging) will
+;; be correctly processed.
+; RUN: opt --try-experimental-debuginfo-iterators -passes=hwasan -S -o - %s | FileCheck %s
+
 target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
 target triple = "aarch64--linux-android"
 
@@ -12,11 +17,11 @@ entry:
   %nodebug2 = alloca ptr
   %nodebug3 = alloca ptr
   %a = alloca ptr
-  %b = alloca ptr
   ; CHECK: @llvm.dbg.declare{{.*}} !DIExpression(DW_OP_LLVM_tag_offset, 32)
   call void @llvm.dbg.declare(metadata ptr %a, metadata !12, metadata !DIExpression()), !dbg !14
   ; CHECK: @llvm.dbg.declare{{.*}} !DIExpression(DW_OP_LLVM_tag_offset, 32)
   call void @llvm.dbg.declare(metadata ptr %a, metadata !12, metadata !DIExpression()), !dbg !14
+  %b = alloca ptr
   ; CHECK: @llvm.dbg.declare{{.*}} !DIExpression(DW_OP_LLVM_tag_offset, 96)
   call void @llvm.dbg.declare(metadata ptr %b, metadata !13, metadata !DIExpression()), !dbg !14
   ; CHECK: @llvm.dbg.declare{{.*}} !DIExpression(DW_OP_LLVM_tag_offset, 96)