[InstCombine] Merge DebugLoc when speculatively hoisting store instruction

Summary: Along with https://reviews.llvm.org/D27804, debug locations need to be merged when hoisting store instructions as well. Not sure if just dropping debug locations would make more sense for this case, but as the branch instruction will have at least different discriminator with the hoisted store instruction, I think there will be no difference in practice.

Reviewers: aprantl, andreadb, danielcdh

Reviewed By: aprantl

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D29062

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@293372 91177308-0d34-0410-b5e6-96231b3b80d8

Author: taewookoh

lib/Transforms/Utils/SimplifyCFG.cpp

@@ -1280,7 +1280,7 @@ static bool HoistThenElseCodeToIf(BranchInst *BI,
     if (!isa<CallInst>(I1))
       I1->setDebugLoc(
           DILocation::getMergedLocation(I1->getDebugLoc(), I2->getDebugLoc()));
- 
+
     I2->eraseFromParent();
     Changed = true;
 
@@ -1546,7 +1546,7 @@ static bool sinkLastInstruction(ArrayRef<BasicBlock*> Blocks) {
         }))
       return false;
   }
-  
+
   // We don't need to do any more checking here; canSinkLastInstruction should
   // have done it all for us.
   SmallVector<Value*, 4> NewOperands;
@@ -1653,7 +1653,7 @@ namespace {
     bool isValid() const {
       return !Fail;
     }
-    
+
     void operator -- () {
       if (Fail)
         return;
@@ -1737,7 +1737,7 @@ static bool SinkThenElseCodeToEnd(BranchInst *BI1) {
   }
   if (UnconditionalPreds.size() < 2)
     return false;
-  
+
   bool Changed = false;
   // We take a two-step approach to tail sinking. First we scan from the end of
   // each block upwards in lockstep. If the n'th instruction from the end of each
@@ -1767,7 +1767,7 @@ static bool SinkThenElseCodeToEnd(BranchInst *BI1) {
     unsigned NumPHIInsts = NumPHIdValues / UnconditionalPreds.size();
     if ((NumPHIdValues % UnconditionalPreds.size()) != 0)
         NumPHIInsts++;
-    
+
     return NumPHIInsts <= 1;
   };
 
@@ -1790,7 +1790,7 @@ static bool SinkThenElseCodeToEnd(BranchInst *BI1) {
     }
     if (!Profitable)
       return false;
-    
+
     DEBUG(dbgs() << "SINK: Splitting edge\n");
     // We have a conditional edge and we're going to sink some instructions.
     // Insert a new block postdominating all blocks we're going to sink from.
@@ -1800,7 +1800,7 @@ static bool SinkThenElseCodeToEnd(BranchInst *BI1) {
       return false;
     Changed = true;
   }
-  
+
   // Now that we've analyzed all potential sinking candidates, perform the
   // actual sink. We iteratively sink the last non-terminator of the source
   // blocks into their common successor unless doing so would require too
@@ -1826,7 +1826,7 @@ static bool SinkThenElseCodeToEnd(BranchInst *BI1) {
       DEBUG(dbgs() << "SINK: stopping here, too many PHIs would be created!\n");
       break;
     }
-    
+
     if (!sinkLastInstruction(UnconditionalPreds))
       return Changed;
     NumSinkCommons++;
@@ -2078,6 +2078,9 @@ static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *ThenBB,
     Value *S = Builder.CreateSelect(
         BrCond, TrueV, FalseV, TrueV->getName() + "." + FalseV->getName(), BI);
     SpeculatedStore->setOperand(0, S);
+    SpeculatedStore->setDebugLoc(
+        DILocation::getMergedLocation(
+          BI->getDebugLoc(), SpeculatedStore->getDebugLoc()));
   }
 
   // Metadata can be dependent on the condition we are hoisting above.

test/Transforms/SimplifyCFG/remove-debug-2.ll

@@ -0,0 +1,68 @@
+; RUN: opt < %s -simplifycfg -S | FileCheck %s
+
+; Check if the debug info for hoisted store for "ret = 0" is removed
+;
+; int foo(int x) {
+;   int ret = 1;
+;   if (x)
+;     ret = 0;
+;   return ret;
+; }
+;
+; CHECK: store i32 1,{{.+}}!dbg ![[DLOC1:[0-9]+]]
+; CHECK: icmp ne {{.+}}!dbg ![[DLOC2:[0-9]+]]
+; CHECK: [[VREG:%[^ ]+]] = select
+; CHECK: store i32 [[VREG]]
+; CHECK-NOT: !dbg
+; CHECK-SAME: {{$}}
+; CHECK: ret {{.+}}!dbg ![[DLOC3:[0-9]+]]
+; CHECK: ![[DLOC1]] = !DILocation(line: 2
+; CHECK: ![[DLOC2]] = !DILocation(line: 3
+; CHECK: ![[DLOC3]] = !DILocation(line: 5
+
+target triple = "x86_64-unknown-linux-gnu"
+
+; Function Attrs: noinline nounwind uwtable
+define i32 @foo(i32) !dbg !6 {
+  %2 = alloca i32, align 4
+  %3 = alloca i32, align 4
+  store i32 %0, i32* %2, align 4
+  store i32 1, i32* %3, align 4, !dbg !14
+  %4 = load i32, i32* %2, align 4, !dbg !15
+  %5 = icmp ne i32 %4, 0, !dbg !15
+  br i1 %5, label %6, label %7, !dbg !17
+
+; <label>:6:                                      ; preds = %1
+  store i32 0, i32* %3, align 4, !dbg !18
+  br label %7, !dbg !19
+
+; <label>:7:                                      ; preds = %6, %1
+  %8 = load i32, i32* %3, align 4, !dbg !20
+  ret i32 %8, !dbg !21
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1)
+!1 = !DIFile(filename: "foo.c", directory: "b/")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{}
+!6 = distinct !DISubprogram(name: "foo", scope: !1, file: !1, line: 1, type: !7, isLocal: false, isDefinition: true, scopeLine: 1, flags: DIFlagPrototyped, isOptimized: false, unit: !0, variables: !2)
+!7 = !DISubroutineType(types: !8)
+!8 = !{!9, !9}
+!9 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!10 = !DILocalVariable(name: "x", arg: 1, scope: !6, file: !1, line: 1, type: !9)
+!11 = !DIExpression()
+!12 = !DILocation(line: 1, column: 13, scope: !6)
+!13 = !DILocalVariable(name: "ret", scope: !6, file: !1, line: 2, type: !9)
+!14 = !DILocation(line: 2, column: 7, scope: !6)
+!15 = !DILocation(line: 3, column: 7, scope: !16)
+!16 = distinct !DILexicalBlock(scope: !6, file: !1, line: 3, column: 7)
+!17 = !DILocation(line: 3, column: 7, scope: !6)
+!18 = !DILocation(line: 4, column: 9, scope: !16)
+!19 = !DILocation(line: 4, column: 5, scope: !16)
+!20 = !DILocation(line: 5, column: 10, scope: !6)
+!21 = !DILocation(line: 5, column: 3, scope: !6)