[GVN, OptDiag] Print the interesting instructions involved in missed load-elimination

[recommitting after the fix in r288307]

This includes the intervening store and the load/store that we're trying
to forward from in the optimization remark for the missed load
elimination.

This is hooked up under a new mode in ORE that allows for compile-time
budget for a bit more analysis to print more insightful messages.  This
mode is currently enabled for -fsave-optimization-record (-Rpass is
trickier since it is controlled in the front-end).

With this we can now print the red remark in http://lab.llvm.org:8080/artifacts/opt-view_test-suite/build/SingleSource/Benchmarks/Dhrystone/CMakeFiles/dry.dir/html/_org_test-suite_SingleSource_Benchmarks_Dhrystone_dry.c.html#L446

Differential Revision: https://reviews.llvm.org/D26490

llvm-svn: 288381

1 files changed, 44 insertions, 1 deletions

diff --git a/llvm/test/Transforms/GVN/opt-remarks.ll b/llvm/test/Transforms/GVN/opt-remarks.ll
index 14c1feff4a1..e31793038cb 100644
--- a/llvm/test/Transforms/GVN/opt-remarks.ll
+++ b/llvm/test/Transforms/GVN/opt-remarks.ll
@@ -40,7 +40,22 @@
 ; YAML-NEXT:   - String:          ' in favor of '
 ; YAML-NEXT:   - InfavorOfValue:  load
 ; YAML-NEXT: ...
-
+; YAML-NEXT: --- !Missed
+; YAML-NEXT: Pass:            gvn
+; YAML-NEXT: Name:            LoadClobbered
+; YAML-NEXT: DebugLoc:        { File: /tmp/s.c, Line: 3, Column: 3 }
+; YAML-NEXT: Function:        may_alias
+; YAML-NEXT: Args:
+; YAML-NEXT:   - String:          'load of type '
+; YAML-NEXT:   - Type:            i32
+; YAML-NEXT:   - String:          ' not eliminated'
+; YAML-NEXT:   - String:          ' in favor of '
+; YAML-NEXT:   - OtherAccess:     load
+; YAML-NEXT:     DebugLoc:        { File: /tmp/s.c, Line: 1, Column: 13 }
+; YAML-NEXT:   - String:          ' because it is clobbered by '
+; YAML-NEXT:   - ClobberedBy:     store
+; YAML-NEXT:     DebugLoc:        { File: /tmp/s.c, Line: 2, Column: 10 }
+; YAML-NEXT: ...
 
 define i32 @arg(i32* %p, i32 %i) {
 entry:
@@ -63,3 +78,31 @@ entry:
   %add = add i32 %load1, %load
   ret i32 %add
 }
+
+define i32 @may_alias(i32* %p, i32* %r) !dbg !7 {
+entry:
+  %load1 = load i32, i32* %p, !tbaa !13, !dbg !9
+  store i32 4, i32* %r, !tbaa !13, !dbg !10
+  %load = load i32, i32* %p, !tbaa !13, !dbg !11
+  %add = add i32 %load1, %load
+  ret i32 %add
+}
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4, !5}
+!llvm.ident = !{!6}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 4.0.0 (trunk 282540) (llvm/trunk 282542)", isOptimized: true, runtimeVersion: 0, emissionKind: LineTablesOnly, enums: !2)
+!1 = !DIFile(filename: "/tmp/s.c", directory: "/tmp")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{i32 1, !"PIC Level", i32 2}
+!6 = !{!"clang version 4.0.0 (trunk 282540) (llvm/trunk 282542)"}
+!7 = distinct !DISubprogram(name: "may_alias", scope: !1, file: !1, line: 1, type: !8, isLocal: false, isDefinition: true, scopeLine: 1, isOptimized: true, unit: !0, variables: !2)
+!8 = !DISubroutineType(types: !2)
+!9 = !DILocation(line: 1, column: 13, scope: !7)
+!10 = !DILocation(line: 2, column: 10, scope: !7)
+!11 = !DILocation(line: 3, column: 3, scope: !7)
+
+!12 = !{ !"tbaa root" }
+!13 = !{ !"int", !12 }