[DebugInfo@O2][LoopVectorize] pr39024: Vectorized code linenos step through loop even after completion

Summary:
Bug: https://bugs.llvm.org/show_bug.cgi?id=39024

The bug reports that a vectorized loop is stepped through 4 times and each step through the loop seemed to show a different path. I found two problems here:

A) An incorrect line number on a preheader block (for.body.preheader) instruction causes a step into the loop before it begins.
B) Instructions in the middle block have different line numbers which give the impression of another iteration.

In this patch I give all of the middle block instructions the line number of the scalar loop latch terminator branch. This seems to provide the smoothest debugging experience because the vectorized loops will always end on this line before dropping into the scalar loop. To solve problem A I have altered llvm::SplitBlockPredecessors to accommodate loop header blocks.

Reviewers: samsonov, vsk, aprantl, probinson, anemet, hfinkel

Reviewed By: hfinkel

Subscribers: bjope, jmellorcrummey, hfinkel, gbedwell, hiraditya, zzheng, llvm-commits

Tags: #llvm, #debug-info

Differential Revision: https://reviews.llvm.org/D60831

llvm-svn: 360162

2 files changed, 8 insertions, 8 deletions

diff --git a/llvm/test/Transforms/LoopVectorize/X86/vectorization-remarks-missed.ll b/llvm/test/Transforms/LoopVectorize/X86/vectorization-remarks-missed.ll
index 4aa96df94ff..a90ce99268b 100644
--- a/llvm/test/Transforms/LoopVectorize/X86/vectorization-remarks-missed.ll
+++ b/llvm/test/Transforms/LoopVectorize/X86/vectorization-remarks-missed.ll
@@ -16,15 +16,15 @@
 ;   }
 ; }
 ; File, line, and column should match those specified in the metadata
-; CHECK: remark: source.cpp:4:5: loop not vectorized: could not determine number of loop iterations
-; CHECK: remark: source.cpp:4:5: loop not vectorized
+; CHECK: remark: source.cpp:5:9: loop not vectorized: could not determine number of loop iterations
+; CHECK: remark: source.cpp:5:9: loop not vectorized
 
 ; void test_disabled(int *A, int Length) {
 ; #pragma clang loop vectorize(disable) interleave(disable)
 ;   for (int i = 0; i < Length; i++)
 ;     A[i] = i;
 ; }
-; CHECK: remark: source.cpp:13:5: loop not vectorized: vectorization and interleaving are explicitly disabled, or the loop has already been vectorized
+; CHECK: remark: source.cpp:12:8: loop not vectorized: vectorization and interleaving are explicitly disabled, or the loop has already been vectorized
 
 ; void test_array_bounds(int *A, int *B, int Length) {
 ; #pragma clang loop vectorize(enable)
@@ -51,7 +51,7 @@
 ; YAML:       --- !Analysis
 ; YAML-NEXT: Pass:            loop-vectorize
 ; YAML-NEXT: Name:            CantComputeNumberOfIterations
-; YAML-NEXT: DebugLoc:        { File: source.cpp, Line: 4, Column: 5 }
+; YAML-NEXT: DebugLoc:        { File: source.cpp, Line: 5, Column: 9 }
 ; YAML-NEXT: Function:        _Z4testPii
 ; YAML-NEXT: Args:
 ; YAML-NEXT:   - String:          'loop not vectorized: '
@@ -60,7 +60,7 @@
 ; YAML-NEXT: --- !Missed
 ; YAML-NEXT: Pass:            loop-vectorize
 ; YAML-NEXT: Name:            MissedDetails
-; YAML-NEXT: DebugLoc:        { File: source.cpp, Line: 4, Column: 5 }
+; YAML-NEXT: DebugLoc:        { File: source.cpp, Line: 5, Column: 9 }
 ; YAML-NEXT: Function:        _Z4testPii
 ; YAML-NEXT: Args:
 ; YAML-NEXT:   - String:          loop not vectorized
@@ -68,7 +68,7 @@
 ; YAML-NEXT: --- !Analysis
 ; YAML-NEXT: Pass:            loop-vectorize
 ; YAML-NEXT: Name:            AllDisabled
-; YAML-NEXT: DebugLoc:        { File: source.cpp, Line: 13, Column: 5 }
+; YAML-NEXT: DebugLoc:        { File: source.cpp, Line: 12, Column: 8 }
 ; YAML-NEXT: Function:        _Z13test_disabledPii
 ; YAML-NEXT: Args:
 ; YAML-NEXT:   - String:          'loop not vectorized: vectorization and interleaving are explicitly disabled, or the loop has already been vectorized
diff --git a/llvm/test/Transforms/LoopVectorize/X86/vectorization-remarks-profitable.ll b/llvm/test/Transforms/LoopVectorize/X86/vectorization-remarks-profitable.ll
index ac0648a6838..228515efc70 100644
--- a/llvm/test/Transforms/LoopVectorize/X86/vectorization-remarks-profitable.ll
+++ b/llvm/test/Transforms/LoopVectorize/X86/vectorization-remarks-profitable.ll
@@ -3,8 +3,8 @@
 ; Verify analysis remarks are generated when interleaving is not beneficial.
 ; CHECK: remark: vectorization-remarks-profitable.c:5:17: the cost-model indicates that vectorization is not beneficial
 ; CHECK: remark: vectorization-remarks-profitable.c:5:17: the cost-model indicates that interleaving is not beneficial and is explicitly disabled or interleave count is set to 1
-; CHECK: remark: vectorization-remarks-profitable.c:12:17: the cost-model indicates that vectorization is not beneficial
-; CHECK: remark: vectorization-remarks-profitable.c:12:17: the cost-model indicates that interleaving is not beneficial
+; CHECK: remark: vectorization-remarks-profitable.c:11:3: the cost-model indicates that vectorization is not beneficial
+; CHECK: remark: vectorization-remarks-profitable.c:11:3: the cost-model indicates that interleaving is not beneficial
 
 ; First loop.
 ;  #pragma clang loop interleave(disable) unroll(disable)