[llvm] r184881 - Print block frequencies in decimal form.

[Robinson, Paul]

> Author: stoklund
> Date: Tue Jun 25 16:57:38 2013
> New Revision: 184881
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=184881&view=rev
> Log:
> Print block frequencies in decimal form.
> 
> This is easier to read than the internal fixed-point representation.
> 
> If anybody knows the correct algorithm for converting fixed-point
> numbers to base 10, feel free to fix it.

The correct algorithm is to use a power-of-10 scale factor. :-)

I took a quick look through BlockFrequency.h/.cpp and didn't see
any reason why ENTRY_FREQ could not be 1000 instead of 1024.
The only arithmetic on pairs of frequencies is add/subtract so
the scale factor is irrelevant to all the math operations.
(I owned a COBOL compiler for a number of years; I know my way
around decimal data.)

Then if you don't mind trailing zeros, the print function becomes:

>  void BlockFrequency::print(raw_ostream &OS) const {
> -  OS << Frequency;
> +  // Convert fixed-point number to decimal.
> +  OS << Frequency / getEntryFrequency() << "."
> +     << Frequency % getEntryFrequency();
>  }

And if you do mind trailing zeros, it's a little tedious but
not hard.

--paulr

> 
> Modified:
>     llvm/trunk/lib/Support/BlockFrequency.cpp
>     llvm/trunk/test/Analysis/BlockFrequencyInfo/basic.ll
> 
> Modified: llvm/trunk/lib/Support/BlockFrequency.cpp
> URL: http://llvm.org/viewvc/llvm-
> project/llvm/trunk/lib/Support/BlockFrequency.cpp?rev=184881&r1=184880&r
> 2=184881&view=diff
> ========================================================================
> ======
> --- llvm/trunk/lib/Support/BlockFrequency.cpp (original)
> +++ llvm/trunk/lib/Support/BlockFrequency.cpp Tue Jun 25 16:57:38 2013
> @@ -117,7 +117,16 @@ BlockFrequency::operator+(const BlockFre
>  }
> 
>  void BlockFrequency::print(raw_ostream &OS) const {
> -  OS << Frequency;
> +  // Convert fixed-point number to decimal.
> +  OS << Frequency / getEntryFrequency() << ".";
> +  uint64_t Rem = Frequency % getEntryFrequency();
> +  uint64_t Eps = 1;
> +  do {
> +    Rem *= 10;
> +    Eps *= 10;
> +    OS << Rem / getEntryFrequency();
> +    Rem = Rem % getEntryFrequency();
> +  } while (Rem >= Eps/2);
>  }
> 
>  namespace llvm {
> 
> Modified: llvm/trunk/test/Analysis/BlockFrequencyInfo/basic.ll
> URL: http://llvm.org/viewvc/llvm-
> project/llvm/trunk/test/Analysis/BlockFrequencyInfo/basic.ll?rev=184881&
> r1=184880&r2=184881&view=diff
> ========================================================================
> ======
> --- llvm/trunk/test/Analysis/BlockFrequencyInfo/basic.ll (original)
> +++ llvm/trunk/test/Analysis/BlockFrequencyInfo/basic.ll Tue Jun 25
> 16:57:38 2013
> @@ -2,12 +2,12 @@
> 
>  define i32 @test1(i32 %i, i32* %a) {
>  ; CHECK: Printing analysis {{.*}} for function 'test1'
> -; CHECK: entry = 16384
> +; CHECK: entry = 1.0
>  entry:
>    br label %body
> 
>  ; Loop backedges are weighted and thus their bodies have a greater
> frequency.
> -; CHECK: body = 524288
> +; CHECK: body = 32.0
>  body:
>    %iv = phi i32 [ 0, %entry ], [ %next, %body ]
>    %base = phi i32 [ 0, %entry ], [ %sum, %body ]
> @@ -18,29 +18,29 @@ body:
>    %exitcond = icmp eq i32 %next, %i
>    br i1 %exitcond, label %exit, label %body
> 
> -; CHECK: exit = 16384
> +; CHECK: exit = 1.0
>  exit:
>    ret i32 %sum
>  }
> 
>  define i32 @test2(i32 %i, i32 %a, i32 %b) {
>  ; CHECK: Printing analysis {{.*}} for function 'test2'
> -; CHECK: entry = 16384
> +; CHECK: entry = 1.0
>  entry:
>    %cond = icmp ult i32 %i, 42
>    br i1 %cond, label %then, label %else, !prof !0
> 
>  ; The 'then' branch is predicted more likely via branch weight
> metadata.
> -; CHECK: then = 15420
> +; CHECK: then = 0.94116
>  then:
>    br label %exit
> 
> -; CHECK: else = 963
> +; CHECK: else = 0.05877
>  else:
>    br label %exit
> 
> -; FIXME: It may be a bug that we don't sum back to 16384.
> -; CHECK: exit = 16383
> +; FIXME: It may be a bug that we don't sum back to 1.0.
> +; CHECK: exit = 0.99993
>  exit:
>    %result = phi i32 [ %a, %then ], [ %b, %else ]
>    ret i32 %result
> @@ -50,36 +50,36 @@ exit:
> 
>  define i32 @test3(i32 %i, i32 %a, i32 %b, i32 %c, i32 %d, i32 %e) {
>  ; CHECK: Printing analysis {{.*}} for function 'test3'
> -; CHECK: entry = 16384
> +; CHECK: entry = 1.0
>  entry:
>    switch i32 %i, label %case_a [ i32 1, label %case_b
>                                   i32 2, label %case_c
>                                   i32 3, label %case_d
>                                   i32 4, label %case_e ], !prof !1
> 
> -; CHECK: case_a = 819
> +; CHECK: case_a = 0.04998
>  case_a:
>    br label %exit
> 
> -; CHECK: case_b = 819
> +; CHECK: case_b = 0.04998
>  case_b:
>    br label %exit
> 
>  ; The 'case_c' branch is predicted more likely via branch weight
> metadata.
> -; CHECK: case_c = 13107
> +; CHECK: case_c = 0.79998
>  case_c:
>    br label %exit
> 
> -; CHECK: case_d = 819
> +; CHECK: case_d = 0.04998
>  case_d:
>    br label %exit
> 
> -; CHECK: case_e = 819
> +; CHECK: case_e = 0.04998
>  case_e:
>    br label %exit
> 
> -; FIXME: It may be a bug that we don't sum back to 16384.
> -; CHECK: exit = 16383
> +; FIXME: It may be a bug that we don't sum back to 1.0.
> +; CHECK: exit = 0.99993
>  exit:
>    %result = phi i32 [ %a, %case_a ],
>                      [ %b, %case_b ],
> 
> 
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