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  1. Apr 23, 2008
  2. Apr 22, 2008
    • Chris Lattner's avatar
      Start doing the significantly useful part of jump threading: handle cases · 37e9c187
      Chris Lattner authored
      where a comparison has a phi input and that phi is a constant.  For example,
      stuff like:
      
        Threading edge through bool from 'bb2149' to 'bb2231' with cost: 1, across block:
      bb2237:		; preds = %bb2231, %bb2149
      	%tmp2328.rle = phi i32 [ %tmp2232, %bb2231 ], [ %tmp2232439, %bb2149 ]		; <i32> [#uses=2]
      	%done.0 = phi i32 [ %done.2, %bb2231 ], [ 0, %bb2149 ]		; <i32> [#uses=1]
      	%tmp2239 = icmp eq i32 %done.0, 0		; <i1> [#uses=1]
      	br i1 %tmp2239, label %bb2231, label %bb2327
      
      or
      
      bb38.i298:		; preds = %bb33.i295, %bb1693
      	%tmp39.i296.rle = phi %struct.ibox* [ null, %bb1693 ], [ %tmp39.i296.rle1109, %bb33.i295 ]		; <%struct.ibox*> [#uses=2]
      	%minspan.1.i291.reg2mem.1 = phi i32 [ 32000, %bb1693 ], [ %minspan.0.i288, %bb33.i295 ]		; <i32> [#uses=1]
      	%tmp40.i297 = icmp eq %struct.ibox* %tmp39.i296.rle, null		; <i1> [#uses=1]
      	br i1 %tmp40.i297, label %implfeeds.exit311, label %bb43.i301
      
      This triggers thousands of times in spec.
      
      llvm-svn: 50110
      37e9c187
    • Chris Lattner's avatar
      Dig through multiple levels of AND to thread jumps if needed. · d5425e8f
      Chris Lattner authored
      llvm-svn: 50106
      d5425e8f
    • Chris Lattner's avatar
      Teach jump threading to thread through blocks like: · 3df4c15d
      Chris Lattner authored
        br (and X, phi(Y, Z, false)), label L1, label L2
      
      This triggers once on 252.eon and 6 times on 176.gcc.  Blocks 
      in question often look like this:
      
      bb262:		; preds = %bb261, %bb248
      	%iftmp.251.0 = phi i1 [ true, %bb261 ], [ false, %bb248 ]		; <i1> [#uses=4]
      	%tmp270 = icmp eq %struct.rtx_def* %tmp.0.i, null		; <i1> [#uses=1]
      	%bothcond = or i1 %iftmp.251.0, %tmp270		; <i1> [#uses=1]
      	br i1 %bothcond, label %bb288, label %bb273
      
      In this case, it is clear that it doesn't matter if tmp.0.i is null when coming from bb261.  When coming from bb248, it is all that matters.
      
      
      Another random example:
      
      check_asm_operands.exit:		; preds = %check_asm_operands.exit.thr_comm, %bb30.i, %bb12.i, %bb6.i413
      	%tmp.0.i420 = phi i1 [ true, %bb6.i413 ], [ true, %bb12.i ], [ true, %bb30.i ], [ false, %check_asm_operands.exit.thr_comm ; <i1> [#uses=1]
      	call void @llvm.stackrestore( i8* %savedstack ) nounwind 
      	%tmp4389 = icmp eq i32 %added_sets_1.0, 0		; <i1> [#uses=1]
      	%tmp4394 = icmp eq i32 %added_sets_2.0, 0		; <i1> [#uses=1]
      	%bothcond80 = and i1 %tmp4389, %tmp4394		; <i1> [#uses=1]
      	%bothcond81 = and i1 %bothcond80, %tmp.0.i420		; <i1> [#uses=1]
      	br i1 %bothcond81, label %bb4398, label %bb4397
      
      Here is the case from 252.eon:
      
      bb290.i.i:		; preds = %bb23.i57.i.i, %bb8.i39.i.i, %bb100.i.i, %bb100.i.i, %bb85.i.i110
      	%myEOF.1.i.i = phi i1 [ true, %bb100.i.i ], [ true, %bb100.i.i ], [ true, %bb85.i.i110 ], [ true, %bb8.i39.i.i ], [ false, %bb23.i57.i.i ]		; <i1> [#uses=2]
      	%i.4.i.i = phi i32 [ %i.1.i.i, %bb85.i.i110 ], [ %i.0.i.i, %bb100.i.i ], [ %i.0.i.i, %bb100.i.i ], [ %i.3.i.i, %bb8.i39.i.i ], [ %i.3.i.i, %bb23.i57.i.i ]		; <i32> [#uses=3]
      	%tmp292.i.i = load i8* %tmp16.i.i100, align 1		; <i8> [#uses=1]
      	%tmp293.not.i.i = icmp ne i8 %tmp292.i.i, 0		; <i1> [#uses=1]
      	%bothcond.i.i = and i1 %tmp293.not.i.i, %myEOF.1.i.i		; <i1> [#uses=1]
      	br i1 %bothcond.i.i, label %bb202.i.i, label %bb301.i.i
        Factoring out 3 common predecessors.
      
      On the path from any blocks other than bb23.i57.i.i, the load and compare 
      are dead.
      
      llvm-svn: 50096
      3df4c15d
    • Chris Lattner's avatar
      refactor some code, no functionality change. · e369c35a
      Chris Lattner authored
      llvm-svn: 50094
      e369c35a
    • Chris Lattner's avatar
      remove dead code. · 8fb13cbe
      Chris Lattner authored
      llvm-svn: 50080
      8fb13cbe
    • Chris Lattner's avatar
      optimize "p != gep p, ..." better. This allows us to compile · c3a43935
      Chris Lattner authored
      getelementptr-seteq.ll into:
      
      define i1 @test(i64 %X, %S* %P) {
      	%C = icmp eq i64 %X, -1		; <i1> [#uses=1]
      	ret i1 %C
      }
      
      instead of:
      
      define i1 @test(i64 %X, %S* %P) {
      	%A.idx.mask = and i64 %X, 4611686018427387903		; <i64> [#uses=1]
      	%C = icmp eq i64 %A.idx.mask, 4611686018427387903		; <i1> [#uses=1]
      	ret i1 %C
      }
      
      And fixes the second half of PR2235.  This speeds up the insertion sort
      case by 45%, from 1.12s to 0.77s.  In practice, this will significantly
      speed up for loops structured like:
      
      for (double *P = Base + N; P != Base; --P)
        ...
      
      Which happens frequently for C++ iterators.
      
      llvm-svn: 50079
      c3a43935
    • Chris Lattner's avatar
      more fallout from Nicholas' asmprinter patch. · ff834c0c
      Chris Lattner authored
      llvm-svn: 50078
      ff834c0c
    • Dan Gohman's avatar
      Implement an x86-64 ABI detail of passing structs by hidden first · f166d2d0
      Dan Gohman authored
      argument. The x86-64 ABI requires the incoming value of %rdi to
      be copied to %rax on exit from a function that is returning a
      large C struct.
      
      Also, add a README-X86-64 entry detailing the missed optimization
      opportunity and proposing an alternative approach.
      
      llvm-svn: 50075
      f166d2d0
  3. Apr 21, 2008
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