[DebugInfo] Remove un-necessary logic from HoistThenElseCodeToIf

Following PR39807, the way in which SimplifyCFG hoists common code on
branch paths was fixed in r347782. However this left extra code hanging
around HoistThenElseCodeToIf that wasn't necessary and needlessly
complicated matters -- we no longer need to look up through the 'if'
basic block to find a location for hoisted 'select' insts, we can instead
use the location chosen by applyMergedLocation.

This patch deletes that extra logic, and updates a regression test to
reflect the new logic (selects get the merged location, not a previous
insts location).

Differential Revision: https://reviews.llvm.org/D55272

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@351058 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp
index ac09ce5a347dd3c2305c28985ba3df4367efb887..03b73954321d86861f12058b195505a14e416e93 100644 (file)
--- a/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -1373,14 +1373,6 @@ HoistTerminator:
     }
   }
 
-  // As the parent basic block terminator is a branch instruction which is
-  // removed at the end of the current transformation, use its previous
-  // non-debug instruction, as the reference insertion point, which will
-  // provide the debug location for generated select instructions. For BBs
-  // with only debug instructions, use an empty debug location.
-  Instruction *InsertPt =
-      BIParent->getTerminator()->getPrevNonDebugInstruction();
-
   // Okay, it is safe to hoist the terminator.
   Instruction *NT = I1->clone();
   BIParent->getInstList().insert(BI->getIterator(), NT);
@@ -1394,11 +1386,8 @@ HoistTerminator:
   // it involves inlinable calls.
   NT->applyMergedLocation(I1->getDebugLoc(), I2->getDebugLoc());
 
+  // PHIs created below will adopt NT's merged DebugLoc.
   IRBuilder<NoFolder> Builder(NT);
-  // If an earlier instruction in this BB had a location, adopt it, otherwise
-  // clear debug locations.
-  Builder.SetCurrentDebugLocation(InsertPt ? InsertPt->getDebugLoc()
-                                           : DebugLoc());
 
   // Hoisting one of the terminators from our successor is a great thing.
   // Unfortunately, the successors of the if/else blocks may have PHI nodes in

diff --git a/test/CodeGen/X86/pr39187-g.ll b/test/CodeGen/X86/pr39187-g.ll
index 46da64111224411654c93500a5f6e663138cf663..2c9dcc5dfff35576d7b6aa6043b42c826dd0a923 100644 (file)
--- a/test/CodeGen/X86/pr39187-g.ll
+++ b/test/CodeGen/X86/pr39187-g.ll
@@ -7,22 +7,8 @@
 ; location keep references to its basic block, causing the debug information
 ; to become ambiguous. It causes the debugger to display unreached lines.
 
-; Change the debug location associated with the hoisted instruction, to
-; the debug location from the insertion point in the 'if' block.
-
-; The insertion point is the previous non-debug instruction before the
-; terminator in the parent basic block of the hoisted instruction.
-
-; IR with '-g':
-;
-;  [...]
-;  %frombool = zext i1 %cmp to i8, !dbg !26
-;  call void @llvm.dbg.value(metadata i8 %frombool, metadata !15, metadata !DIExpression()), !dbg !26
-;  call void @llvm.dbg.value(metadata i32 0, metadata !17, metadata !DIExpression()), !dbg !27
-;  br i1 %cmp, label %if.then, label %if.else
-;  [...]
-;
-; Insertion point is: %frombool = zext i1 %cmp to i8, !dbg !26
+; Check that hoisted instructions get unknown-location line numbers -- there
+; is no correct line number for code that has been common'd in this way.
 
 ; IR generated with:
 ; clang -S -g -gno-column-info -O2 -emit-llvm pr39187.cpp -o pr39187-g.ll -mllvm -opt-bisect-limit=10
@@ -54,7 +40,8 @@
 ; CHECK:  %frombool = zext i1 %cmp to i8, !dbg !16
 ; CHECK:  call void @llvm.dbg.value(metadata i8 %frombool, metadata !13, metadata !DIExpression()), !dbg !16
 ; CHECK:  call void @llvm.dbg.value(metadata i32 0, metadata !15, metadata !DIExpression()), !dbg !17
-; CHECK:  %. = select i1 %cmp, i32 8, i32 4, !dbg !16
+; CHECK:  %. = select i1 %cmp, i32 8, i32 4, !dbg ![[MERGEDLOC:[0-9]+]]
+; CHECK:  ![[MERGEDLOC]] = !DILocation(line: 0, scope: !7)
 
 ; ModuleID = 'pr39187.cpp'
 source_filename = "pr39187.cpp"
@@ -77,11 +64,11 @@ entry:
 
 if.then:                                          ; preds = %entry
   call void @llvm.dbg.value(metadata i32 8, metadata !14, metadata !DIExpression()), !dbg !25
-  br label %if.end
+  br label %if.end, !dbg !25
 
 if.else:                                          ; preds = %entry
-  call void @llvm.dbg.value(metadata i32 4, metadata !14, metadata !DIExpression()), !dbg !25
-  br label %if.end
+  call void @llvm.dbg.value(metadata i32 4, metadata !14, metadata !DIExpression()), !dbg !27
+  br label %if.end, !dbg !27
 
 if.end:                                           ; preds = %if.else, %if.then
   %beards.0 = phi i32 [ 8, %if.then ], [ 4, %if.else ]