[llvm] r223193 - Emit the entry block first and the exit block second, then all the blocks in between afterwards. This is what gcc always does, and some out of tree tools depend on that.
Justin Bogner
mail at justinbogner.com
Mon Mar 9 20:48:20 PDT 2015
Nick Lewycky <nicholas at mxc.ca> writes:
> Author: nicholas
> Date: Tue Dec 2 20:45:01 2014
> New Revision: 223193
>
> URL: http://llvm.org/viewvc/llvm-project?rev=223193&view=rev
> Log:
> Emit the entry block first and the exit block second, then all the
> blocks in between afterwards. This is what gcc always does, and some
> out of tree tools depend on that.
Sorry I didn't notice this earlier, but there's something funny going on
here. This makes llvm-cov choke on a simple hello world, as it assumes
that "The last block is always reserved for exit block".
Now, if gcc always emits the exit block second, this assumption makes no
sense, in which case I'll fix up llvm-cov. However, it looks like this
assumption did make sense back in the gcov-4.2 era, which warns that
each function "has arcs from exit block" with this change. I'm guessing
this behaviour changed (from "last" to "second") in some update of the
format, and that we should not be doing this when emitting a format
version of "402*".
Do you have any insight into this?
> Added:
> llvm/trunk/test/Transforms/GCOVProfiling/return-block.ll
> Modified:
> llvm/trunk/lib/Transforms/Instrumentation/GCOVProfiling.cpp
>
> Modified: llvm/trunk/lib/Transforms/Instrumentation/GCOVProfiling.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Instrumentation/GCOVProfiling.cpp?rev=223193&r1=223192&r2=223193&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Transforms/Instrumentation/GCOVProfiling.cpp (original)
> +++ llvm/trunk/lib/Transforms/Instrumentation/GCOVProfiling.cpp Tue Dec 2 20:45:01 2014
> @@ -310,11 +310,15 @@ namespace {
>
> Function *F = SP.getFunction();
> DEBUG(dbgs() << "Function: " << getFunctionName(SP) << "\n");
> - uint32_t i = 0;
> - for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
> +
> + Function::iterator BB = F->begin(), E = F->end();
> + Blocks[BB++] = new GCOVBlock(0, os);
> + ReturnBlock = new GCOVBlock(1, os);
> +
> + uint32_t i = 2;
> + for (; BB != E; ++BB) {
> Blocks[BB] = new GCOVBlock(i++, os);
> }
> - ReturnBlock = new GCOVBlock(i++, os);
>
> std::string FunctionNameAndLine;
> raw_string_ostream FNLOS(FunctionNameAndLine);
>
> Added: llvm/trunk/test/Transforms/GCOVProfiling/return-block.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/GCOVProfiling/return-block.ll?rev=223193&view=auto
> ==============================================================================
> --- llvm/trunk/test/Transforms/GCOVProfiling/return-block.ll (added)
> +++ llvm/trunk/test/Transforms/GCOVProfiling/return-block.ll Tue Dec 2 20:45:01 2014
> @@ -0,0 +1,66 @@
> +; Inject metadata to set the .gcno file location
> +; RUN: echo '!19 = metadata !{metadata !"%/T/return-block.ll", metadata !0}' > %t1
> +; RUN: cat %s %t1 > %t2
> +; RUN: opt -insert-gcov-profiling -disable-output %t2
> +; RUN: llvm-cov gcov -n -dump return-block.gcno 2>&1 | FileCheck %s
> +
> +target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
> +target triple = "x86_64-unknown-linux-gnu"
> +
> + at A = common global i32 0, align 4
> +
> +; Function Attrs: nounwind uwtable
> +define void @test() #0 {
> +entry:
> + tail call void (...)* @f() #2, !dbg !14
> + %0 = load i32* @A, align 4, !dbg !15
> + %tobool = icmp eq i32 %0, 0, !dbg !15
> + br i1 %tobool, label %if.end, label %if.then, !dbg !15
> +
> +if.then: ; preds = %entry
> + tail call void (...)* @g() #2, !dbg !16
> + br label %if.end, !dbg !16
> +
> +if.end: ; preds = %entry, %if.then
> + ret void, !dbg !18
> +}
> +
> +declare void @f(...) #1
> +
> +declare void @g(...) #1
> +
> +attributes #0 = { nounwind uwtable "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
> +attributes #1 = { "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
> +attributes #2 = { nounwind }
> +
> +!llvm.gcov = !{!14}
> +!llvm.dbg.cu = !{!0}
> +!llvm.module.flags = !{!11, !12}
> +!llvm.ident = !{!13}
> +
> +!0 = metadata !{metadata !"0x11\0012\00clang version 3.6.0 (trunk 223182)\001\00\000\00\001", metadata !1, metadata !2, metadata !2, metadata !3, metadata !8, metadata !2} ; [ DW_TAG_compile_unit ] [return-block.c] [DW_LANG_C99]
> +!1 = metadata !{metadata !".../llvm/test/Transforms/GCOVProfiling/return-block.ll", metadata !""}
> +!2 = metadata !{}
> +!3 = metadata !{metadata !4}
> +!4 = metadata !{metadata !"0x2e\00test\00test\00\005\000\001\000\000\000\001\005", metadata !1, metadata !5, metadata !6, null, void ()* @test, null, null, metadata !2} ; [ DW_TAG_subprogram ] [line 5] [def] [test]
> +!5 = metadata !{metadata !"0x29", metadata !1} ; [ DW_TAG_file_type ] [return-block.c]
> +!6 = metadata !{metadata !"0x15\00\000\000\000\000\000\000", null, null, null, metadata !7, null, null, null} ; [ DW_TAG_subroutine_type ] [line 0, size 0, align 0, offset 0] [from ]
> +!7 = metadata !{null}
> +!8 = metadata !{metadata !9}
> +!9 = metadata !{metadata !"0x34\00A\00A\00\003\000\001", null, metadata !5, metadata !10, i32* @A, null} ; [ DW_TAG_variable ] [A] [line 3] [def]
> +!10 = metadata !{metadata !"0x24\00int\000\0032\0032\000\000\005", null, null} ; [ DW_TAG_base_type ] [int] [line 0, size 32, align 32, offset 0, enc DW_ATE_signed]
> +!11 = metadata !{i32 2, metadata !"Dwarf Version", i32 4}
> +!12 = metadata !{i32 2, metadata !"Debug Info Version", i32 2}
> +!13 = metadata !{metadata !"clang version 3.6.0 (trunk 223182)"}
> +!14 = metadata !{i32 6, i32 3, metadata !4, null}
> +!15 = metadata !{i32 7, i32 7, metadata !4, null}
> +!16 = metadata !{i32 8, i32 5, metadata !17, null}
> +!17 = metadata !{metadata !"0xb\007\007\000", metadata !1, metadata !4} ; [ DW_TAG_lexical_block ] [return-block.c]
> +!18 = metadata !{i32 9, i32 1, metadata !4, null}
> +
> +; There should be no destination edges for block 1.
> +; CHECK: Block : 0 Counter : 0
> +; CHECK-NEXT: Destination Edges : 2 (0),
> +; CHECK-NEXT: Block : 1 Counter : 0
> +; CHECK-NEXT: Source Edges : 4 (0),
> +; CHECK-NEXT: Block : 2 Counter : 0
>
>
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