[LV] Report multiple reasons for not vectorizing under allowExtraAnalysis

The default behavior of -Rpass-analysis=loop-vectorizer is to report only the
first reason encountered for not vectorizing, if one is found, at which time the
vectorizer aborts its handling of the loop. This patch allows multiple reasons
for not vectorizing to be identified and reported, at the potential expense of
additional compile-time, under allowExtraAnalysis which can currently be turned
on by Clang's -fsave-optimization-record and opt's -pass-remarks-missed.

Removed from LoopVectorizationLegality::canVectorize() the redundant checking
and reporting if we CantComputeNumberOfIterations, as LAI::canAnalyzeLoop() also
does that. This redundancy is caught by a lit test once multiple reasons are
reported.

Patch initially developed by Dror Barak.

Differential Revision: https://reviews.llvm.org/D33396

llvm-svn: 303613

1 files changed, 108 insertions, 16 deletions

diff --git a/llvm/test/Transforms/LoopVectorize/X86/vectorization-remarks-missed.ll b/llvm/test/Transforms/LoopVectorize/X86/vectorization-remarks-missed.ll
index b2933c4b56f..4dc62d86453 100644
--- a/llvm/test/Transforms/LoopVectorize/X86/vectorization-remarks-missed.ll
+++ b/llvm/test/Transforms/LoopVectorize/X86/vectorization-remarks-missed.ll
@@ -11,38 +11,38 @@
 ;       break;
 ;   }
 ; }
+; 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
 
 ; 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 vectorize width and interleave count are both set to 1
 
 ; void test_array_bounds(int *A, int *B, int Length) {
 ; #pragma clang loop vectorize(enable)
 ;   for (int i = 0; i < Length; i++)
 ;     A[i] = A[B[i]];
 ; }
-
-; 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:13:5: loop not vectorized: vectorization and interleaving are explicitly disabled, or vectorize width and interleave count are both set to 1
 ; CHECK: remark: source.cpp:19:5: loop not vectorized: cannot identify array bounds
 ; CHECK: remark: source.cpp:19:5: loop not vectorized
 ; CHECK: warning: source.cpp:19:5: loop not vectorized: failed explicitly specified loop vectorization
 
-; CHECK: _Z4testPii
-; CHECK-NOT: x i32>
-; CHECK: ret
-
-; CHECK: _Z13test_disabledPii
-; CHECK-NOT: x i32>
-; CHECK: ret
-
-; CHECK: _Z17test_array_boundsPiS_i
-; CHECK-NOT: x i32>
-; CHECK: ret
+; int foo();
+; void test_multiple_failures(int *A) {
+;   int k = 0;
+; #pragma clang loop vectorize(enable) interleave(enable)
+;   for (int i = 0; i < 1000; i+=A[i]) {
+;     if (A[i])
+;       k = foo();
+;   }
+;   return k;
+; }
+; CHECK: remark: source.cpp:29:7: loop not vectorized: control flow cannot be substituted for a select
+; CHECK: remark: source.cpp:27:3: loop not vectorized
 
 ; YAML:       --- !Analysis
 ; YAML-NEXT: Pass:            loop-vectorize
@@ -98,6 +98,41 @@
 ; YAML-NEXT:   - String:          'loop not vectorized: '
 ; YAML-NEXT:   - String:          failed explicitly specified loop vectorization
 ; YAML-NEXT: ...
+; YAML-NEXT: --- !Analysis
+; YAML-NEXT: Pass:            loop-vectorize
+; YAML-NEXT: Name:            NoCFGForSelect
+; YAML-NEXT: DebugLoc:        { File: source.cpp, Line: 29, Column: 7 }
+; YAML-NEXT: Function:        test_multiple_failures
+; YAML-NEXT: Args:
+; YAML-NEXT:   - String:          'loop not vectorized: '
+; YAML-NEXT:   - String:          control flow cannot be substituted for a select
+; YAML-NEXT: ...
+; YAML-NEXT: --- !Analysis
+; YAML-NEXT: Pass:            loop-vectorize
+; YAML-NEXT: Name:            NonReductionValueUsedOutsideLoop
+; YAML-NEXT: DebugLoc:        { File: source.cpp, Line: 27, Column: 3 }
+; YAML-NEXT: Function:        test_multiple_failures
+; YAML-NEXT: Args:
+; YAML-NEXT:   - String:          'loop not vectorized: '
+; YAML-NEXT:   - String:          value that could not be identified as reduction is used outside the loop
+; YAML-NEXT: ...
+; YAML-NEXT: --- !Analysis
+; YAML-NEXT: Pass:            loop-vectorize
+; YAML-NEXT: Name:            CantComputeNumberOfIterations
+; YAML-NEXT: DebugLoc:        { File: source.cpp, Line: 27, Column: 3 }
+; YAML-NEXT: Function:        test_multiple_failures
+; YAML-NEXT: Args:
+; YAML-NEXT:   - String:          'loop not vectorized: '
+; YAML-NEXT:   - String:          could not determine number of loop iterations
+; YAML-NEXT: ...
+; YAML-NEXT: --- !Missed
+; YAML-NEXT: Pass:            loop-vectorize
+; YAML-NEXT: Name:            MissedDetails
+; YAML-NEXT: DebugLoc:        { File: source.cpp, Line: 27, Column: 3 }
+; YAML-NEXT: Function:        test_multiple_failures
+; YAML-NEXT: Args:
+; YAML-NEXT:   - String:          loop not vectorized
+; YAML-NEXT: ...
 
 target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
 
@@ -124,6 +159,10 @@ for.end:                                          ; preds = %for.body, %entry
   ret void, !dbg !24
 }
 
+; CHECK: _Z4testPii
+; CHECK-NOT: x i32>
+; CHECK: ret
+
 ; Function Attrs: nounwind optsize ssp uwtable
 define void @_Z13test_disabledPii(i32* nocapture %A, i32 %Length) #0 !dbg !7 {
 entry:
@@ -144,6 +183,10 @@ for.end:                                          ; preds = %for.body, %entry
   ret void, !dbg !31
 }
 
+; CHECK: _Z13test_disabledPii
+; CHECK-NOT: x i32>
+; CHECK: ret
+
 ; Function Attrs: nounwind optsize ssp uwtable
 define void @_Z17test_array_boundsPiS_i(i32* nocapture %A, i32* nocapture readonly %B, i32 %Length) #0 !dbg !8 {
 entry:
@@ -174,6 +217,45 @@ for.end:                                          ; preds = %for.end.loopexit, %
   ret void, !dbg !36
 }
 
+; CHECK: _Z17test_array_boundsPiS_i
+; CHECK-NOT: x i32>
+; CHECK: ret
+
+; Function Attrs: nounwind uwtable
+define i32 @test_multiple_failures(i32* nocapture readonly %A) #0 !dbg !46 {
+entry:
+  br label %for.body, !dbg !38
+
+for.body:                                         ; preds = %entry, %for.inc
+  %i.09 = phi i32 [ 0, %entry ], [ %add, %for.inc ]
+  %k.09 = phi i32 [ 0, %entry ], [ %k.1, %for.inc ]
+  %arrayidx = getelementptr inbounds i32, i32* %A, i32 %i.09, !dbg !40
+  %0 = load i32, i32* %arrayidx, align 4, !dbg !40
+  %tobool = icmp eq i32 %0, 0, !dbg !40
+  br i1 %tobool, label %for.inc, label %if.then, !dbg !40
+
+if.then:                                          ; preds = %for.body
+  %call = tail call i32 (...) @foo(), !dbg !41
+  %.pre = load i32, i32* %arrayidx, align 4
+  br label %for.inc, !dbg !42
+
+for.inc:                                          ; preds = %for.body, %if.then
+  %1 = phi i32 [ %.pre, %if.then ], [ 0, %for.body ], !dbg !43
+  %k.1 = phi i32 [ %call, %if.then ], [ %k.09, %for.body ]
+  %add = add nsw i32 %1, %i.09, !dbg !44
+  %cmp = icmp slt i32 %add, 1000, !dbg !45
+  br i1 %cmp, label %for.body, label %for.cond.cleanup, !dbg !38
+
+for.cond.cleanup:                                 ; preds = %for.inc
+  ret i32 %k.1, !dbg !39
+}
+
+declare i32 @foo(...)
+
+; CHECK: test_multiple_failure
+; CHECK-NOT: x i32>
+; CHECK: ret
+
 attributes #0 = { nounwind }
 
 !llvm.dbg.cu = !{!0}
@@ -216,3 +298,13 @@ attributes #0 = { nounwind }
 !34 = !{!34, !15}
 !35 = !DILocation(line: 19, column: 5, scope: !33)
 !36 = !DILocation(line: 20, column: 1, scope: !8)
+!37 = distinct !DILexicalBlock(line: 24, column: 3, file: !1, scope: !46)
+!38 = !DILocation(line: 27, column: 3, scope: !37)
+!39 = !DILocation(line: 31, column: 3, scope: !37)
+!40 = !DILocation(line: 28, column: 9, scope: !37)
+!41 = !DILocation(line: 29, column: 11, scope: !37)
+!42 = !DILocation(line: 29, column: 7, scope: !37)
+!43 = !DILocation(line: 27, column: 32, scope: !37)
+!44 = !DILocation(line: 27, column: 30, scope: !37)
+!45 = !DILocation(line: 27, column: 21, scope: !37)
+!46 = distinct !DISubprogram(name: "test_multiple_failures", line: 26, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: true, unit: !0, scopeLine: 26, file: !1, scope: !5, type: !6, variables: !2)