Skip to content
  1. Oct 18, 2004
  3. Oct 17, 2004
  5. Oct 16, 2004
  7. Oct 13, 2004
  9. Oct 12, 2004
  11. Oct 11, 2004
  13. Oct 09, 2004
  15. Oct 08, 2004
  17. Oct 06, 2004
  19. Sep 29, 2004
  21. Sep 28, 2004
    • Chris Lattner's avatar
      Fold (and (setcc X, C1), (setcc X, C2)) · 623826c8
      Chris Lattner authored 
      This is important for several reasons:

1. Benchmarks have lots of code that looks like this (perlbmk in particular):

  %tmp.2.i = setne int %tmp.0.i, 128              ; <bool> [#uses=1]
  %tmp.6343 = seteq int %tmp.0.i, 1               ; <bool> [#uses=1]
  %tmp.63 = and bool %tmp.2.i, %tmp.6343          ; <bool> [#uses=1]

   we now fold away the setne, a clear improvement.

2. In the more important cases, such as (X >= 10) & (X < 20), we now produce
   smaller code: (X-10) < 10.

3. Perhaps the nicest effect of this patch is that it really helps out the
   code generators.  In particular, for a 'range test' like the above,
   instead of generating this on X86 (the difference on PPC is even more
   pronounced):

        cmp %EAX, 50
        setge %CL
        cmp %EAX, 100
        setl %AL
        and %CL, %AL
        cmp %CL, 0

   we now generate this:

        add %EAX, -50
        cmp %EAX, 50

   Furthermore, this causes setcc's to be folded into branches more often.

These combinations trigger dozens of times in the spec benchmarks, particularly
in 176.gcc, 186.crafty, 253.perlbmk, 254.gap, & 099.go.

llvm-svn: 16559
      623826c8
    • Chris Lattner's avatar
      Implement X / C1 / C2 folding · 272d5ca9
      Chris Lattner authored 
      Implement (setcc (shl X, C1), C2) folding.

The second one occurs several dozen times in spec.  The first was added
just in case.  :)

These are tested by shift.ll:test2[12], and div.ll:test5

llvm-svn: 16549
      272d5ca9
    • Chris Lattner's avatar
      shl is always zero extending, so always use a zero extending shift right. · 6afc02f8
      Chris Lattner authored 
      This latent bug was exposed by recent changes, and is tested as:
llvm/test/Regression/Transforms/InstCombine/2004-09-28-BadShiftAndSetCC.llx

llvm-svn: 16546
      6afc02f8
    • Alkis Evlogimenos's avatar
      Pull assignment out of for loop conditional in order for this to · 3ce42ec7
      Alkis Evlogimenos authored 
      compile under windows. Patch contributed by Paolo Invernizzi!

llvm-svn: 16534
      3ce42ec7
  23. Sep 27, 2004
  25. Sep 24, 2004
  27. Sep 23, 2004
  29. Sep 21, 2004
    • Chris Lattner's avatar
      Do not fold (X + C1 != C2) if there are other users of the add. Doing · b121ae1c
      Chris Lattner authored 
      this transformation used to take a loop like this:

int Array[1000];
void test(int X) {
  int i;
  for (i = 0; i < 1000; ++i)
    Array[i] += X;
}

Compiled to LLVM is:

no_exit:                ; preds = %entry, %no_exit
        %indvar = phi uint [ 0, %entry ], [ %indvar.next, %no_exit ]            ; <uint> [#uses=2]
        %tmp.4 = getelementptr [1000 x int]* %Array, int 0, uint %indvar                ; <int*> [#uses=2]
        %tmp.7 = load int* %tmp.4               ; <int> [#uses=1]
        %tmp.9 = add int %tmp.7, %X             ; <int> [#uses=1]
        store int %tmp.9, int* %tmp.4
***     %indvar.next = add uint %indvar, 1              ; <uint> [#uses=2]
***     %exitcond = seteq uint %indvar.next, 1000               ; <bool> [#uses=1]
        br bool %exitcond, label %return, label %no_exit

and turn it into a loop like this:

no_exit:                ; preds = %entry, %no_exit
        %indvar = phi uint [ 0, %entry ], [ %indvar.next, %no_exit ]            ; <uint> [#uses=3]
        %tmp.4 = getelementptr [1000 x int]* %Array, int 0, uint %indvar                ; <int*> [#uses=2]
        %tmp.7 = load int* %tmp.4               ; <int> [#uses=1]
        %tmp.9 = add int %tmp.7, %X             ; <int> [#uses=1]
        store int %tmp.9, int* %tmp.4
***     %indvar.next = add uint %indvar, 1              ; <uint> [#uses=1]
***     %exitcond = seteq uint %indvar, 999             ; <bool> [#uses=1]
        br bool %exitcond, label %return, label %no_exit

Note that indvar.next and indvar can no longer be coallesced.  In machine
code terms, this patch changes this code:

.LBBtest_1:     # no_exit
        mov %EDX, OFFSET Array
        mov %ESI, %EAX
        add %ESI, DWORD PTR [%EDX + 4*%ECX]
        mov %EDX, OFFSET Array
        mov DWORD PTR [%EDX + 4*%ECX], %ESI
        mov %EDX, %ECX
        inc %EDX
        cmp %ECX, 999
        mov %ECX, %EDX
        jne .LBBtest_1  # no_exit

into this:

.LBBtest_1:     # no_exit
        mov %EDX, OFFSET Array
        mov %ESI, %EAX
        add %ESI, DWORD PTR [%EDX + 4*%ECX]
        mov %EDX, OFFSET Array
        mov DWORD PTR [%EDX + 4*%ECX], %ESI
        inc %ECX
        cmp %ECX, 1000
        jne .LBBtest_1  # no_exit

We need better instruction selection to get this:

.LBBtest_1:     # no_exit
        add DWORD PTR [Array + 4*%ECX], EAX
        inc %ECX
        cmp %ECX, 1000
        jne .LBBtest_1  # no_exit

... but at least there is less register juggling

llvm-svn: 16473
      b121ae1c
  31. Sep 20, 2004