From: Vedant Kumar <vsk@apple.com>
Date: Fri, 19 Apr 2019 22:36:40 +0000 (+0000)
Subject: [GVN+LICM] Use line 0 locations for better crash attribution
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=116c7f3025e46d14d360dfb632ac71fa4a95a26a;p=llvm

[GVN+LICM] Use line 0 locations for better crash attribution

This is a follow-up to r291037+r291258, which used null debug locations
to prevent jumpy line tables.

Using line 0 locations achieves the same effect, but works better for
crash attribution because it preserves the right inline scope.

Differential Revision: https://reviews.llvm.org/D60913

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@358791 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Transforms/Scalar/GVN.cpp b/lib/Transforms/Scalar/GVN.cpp
index 985941eb3c4..f19bb33ae89 100644
--- a/lib/Transforms/Scalar/GVN.cpp
+++ b/lib/Transforms/Scalar/GVN.cpp
@@ -46,6 +46,7 @@
 #include "llvm/IR/Constant.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/DataLayout.h"
+#include "llvm/IR/DebugInfoMetadata.h"
 #include "llvm/IR/DebugLoc.h"
 #include "llvm/IR/Dominators.h"
 #include "llvm/IR/Function.h"
@@ -1206,9 +1207,8 @@ bool GVN::PerformLoadPRE(LoadInst *LI, AvailValInBlkVect &ValuesPerBlock,
     // Instructions that have been inserted in predecessor(s) to materialize
     // the load address do not retain their original debug locations. Doing
     // so could lead to confusing (but correct) source attributions.
-    // FIXME: How do we retain source locations without causing poor debugging
-    // behavior?
-    I->setDebugLoc(DebugLoc());
+    if (const DebugLoc &DL = I->getDebugLoc())
+      I->setDebugLoc(DebugLoc::get(0, 0, DL.getScope(), DL.getInlinedAt()));
 
     // FIXME: We really _ought_ to insert these value numbers into their
     // parent's availability map.  However, in doing so, we risk getting into
diff --git a/lib/Transforms/Scalar/LICM.cpp b/lib/Transforms/Scalar/LICM.cpp
index 31841773375..dcbf2d42c54 100644
--- a/lib/Transforms/Scalar/LICM.cpp
+++ b/lib/Transforms/Scalar/LICM.cpp
@@ -54,6 +54,7 @@
 #include "llvm/IR/CFG.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/DataLayout.h"
+#include "llvm/IR/DebugInfoMetadata.h"
 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/Dominators.h"
 #include "llvm/IR/Instructions.h"
@@ -1652,13 +1653,10 @@ static void hoist(Instruction &I, const DominatorTree *DT, const Loop *CurLoop,
     // Move the new node to the destination block, before its terminator.
     moveInstructionBefore(I, *Dest->getTerminator(), *SafetyInfo, MSSAU);
 
-  // Do not retain debug locations when we are moving instructions to different
-  // basic blocks, because we want to avoid jumpy line tables. Calls, however,
-  // need to retain their debug locs because they may be inlined.
-  // FIXME: How do we retain source locations without causing poor debugging
-  // behavior?
-  if (!isa<CallInst>(I))
-    I.setDebugLoc(DebugLoc());
+  // Apply line 0 debug locations when we are moving instructions to different
+  // basic blocks because we want to avoid jumpy line tables.
+  if (const DebugLoc &DL = I.getDebugLoc())
+    I.setDebugLoc(DebugLoc::get(0, 0, DL.getScope(), DL.getInlinedAt()));
 
   if (isa<LoadInst>(I))
     ++NumMovedLoads;
diff --git a/test/DebugInfo/Generic/licm-hoist-debug-loc.ll b/test/DebugInfo/Generic/licm-hoist-debug-loc.ll
index 77ec4a3f3f0..04429d81e95 100644
--- a/test/DebugInfo/Generic/licm-hoist-debug-loc.ll
+++ b/test/DebugInfo/Generic/licm-hoist-debug-loc.ll
@@ -18,8 +18,9 @@
 ; We make sure that the instruction that is hoisted into the preheader
 ; does not have a debug location.
 ; CHECK: for.body.lr.ph:
-; CHECK: getelementptr{{.*}}%p.addr, i64 4{{$}}
+; CHECK: getelementptr{{.*}}%p.addr, i64 4{{.*}} !dbg [[zero:![0-9]+]]
 ; CHECK: for.body:
+; CHECK: [[zero]] = !DILocation(line: 0
 ;
 ; ModuleID = 't.ll'
 source_filename = "test.c"
diff --git a/test/Transforms/GVN/PRE/phi-translate.ll b/test/Transforms/GVN/PRE/phi-translate.ll
index 02fb8e0626e..81d3d9db522 100644
--- a/test/Transforms/GVN/PRE/phi-translate.ll
+++ b/test/Transforms/GVN/PRE/phi-translate.ll
@@ -4,8 +4,8 @@ target datalayout = "e-p:64:64:64"
 
 ; CHECK-LABEL: @foo(
 ; CHECK: entry.end_crit_edge:
-; CHECK: %[[INDEX:[a-z0-9.]+]] = sext i32 %x to i64{{$}}
-; CHECK: %[[ADDRESS:[a-z0-9.]+]] = getelementptr [100 x i32], [100 x i32]* @G, i64 0, i64 %[[INDEX]]{{$}}
+; CHECK: %[[INDEX:[a-z0-9.]+]] = sext i32 %x to i64{{.*}} !dbg [[ZERO_LOC:![0-9]+]]
+; CHECK: %[[ADDRESS:[a-z0-9.]+]] = getelementptr [100 x i32], [100 x i32]* @G, i64 0, i64 %[[INDEX]]{{.*}} !dbg [[ZERO_LOC]]
 ; CHECK:   %n.pre = load i32, i32* %[[ADDRESS]], !dbg [[N_LOC:![0-9]+]]
 ; CHECK: br label %end
 ; CHECK: then:
@@ -14,7 +14,8 @@ target datalayout = "e-p:64:64:64"
 ; CHECK:   %n = phi i32 [ %n.pre, %entry.end_crit_edge ], [ %z, %then ], !dbg [[N_LOC]]
 ; CHECK:   ret i32 %n
 
-; CHECK: [[N_LOC]] = !DILocation(line: 47, column: 1, scope: !{{.*}})
+; CHECK-DAG: [[N_LOC]] = !DILocation(line: 47, column: 1, scope: !{{.*}})
+; CHECK-DAG: [[ZERO_LOC]] = !DILocation(line: 0
 
 @G = external global [100 x i32]
 define i32 @foo(i32 %x, i32 %z) !dbg !6 {