[llvm-commits] [llvm] r65178 - in /llvm/trunk: lib/Transforms/Scalar/LoopStrengthReduce.cpp test/CodeGen/X86/loop-strength-reduce7.ll

[Dale Johannesen]

On Feb 20, 2009, at 2:16 PMPST, Evan Cheng wrote:

> Author: evancheng
> Date: Fri Feb 20 16:16:49 2009
> New Revision: 65178
>
> URL: http://llvm.org/viewvc/llvm-project?rev=65178&view=rev
> Log:
> Fix strange logic in CollectIVUsers used to determine whether all  
> uses are
> addresses, part 1. This fixes an obvious logic bug. Previously if  
> the only
> in-loop use is a PHI, it would return AllUsesAreAddresses as true.

Yes.   The logic here goes back before I started working on it, but  
that's clearly intentional:

   // If one of the use if a PHI node and all other uses are  
addresses, still
   // allow iv reuse. Essentially we are trading one constant  
multiplication
   // for one fewer iv.
   if (NumPHI > 1)
     AllUsesAreAddresses = false;

although whoever put that in probably should have changed the  
name...are you sure you want to do this?

> Added:
>    llvm/trunk/test/CodeGen/X86/loop-strength-reduce7.ll
> Modified:
>    llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp
>
> Modified: llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp?rev=65178&r1=65177&r2=65178&view=diff
>
> = 
> = 
> = 
> = 
> = 
> = 
> = 
> = 
> ======================================================================
> --- llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp (original)
> +++ llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp Fri Feb  
> 20 16:16:49 2009
> @@ -1439,6 +1439,7 @@
>   // fields of the BasedUsers.  We do this so that it increases the  
> commonality
>   // of the remaining uses.
>   unsigned NumPHI = 0;
> +  bool HasAddress = false;
>   for (unsigned i = 0, e = UsersToProcess.size(); i != e; ++i) {
>     // If the user is not in the current loop, this means it is  
> using the exit
>     // value of the IV.  Do not put anything in the base, make sure  
> it's all in
> @@ -1449,7 +1450,6 @@
>       UsersToProcess[i].Base =
>         SE->getIntegerSCEV(0, UsersToProcess[i].Base->getType());
>     } else {
> -
>       // Addressing modes can be folded into loads and stores.  Be  
> careful that
>       // the store is through the expression, not of the expression  
> though.
>       bool isPHI = false;
> @@ -1462,6 +1462,9 @@
>
>       // Not all uses are outside the loop.
>       AllUsesAreOutsideLoop = false;
> +
> +      if (isAddress)
> +        HasAddress = true;
>
>       // If this use isn't an address, then not all uses are  
> addresses.
>       if (!isAddress && !isPHI)
> @@ -1478,6 +1481,10 @@
>   if (NumPHI > 1)
>     AllUsesAreAddresses = false;
>
> +  // There are no in-loop address uses.
> +  if (AllUsesAreAddresses && (!HasAddress && !AllUsesAreOutsideLoop))
> +    AllUsesAreAddresses = false;
> +
>   return CommonExprs;
> }
>
>
> Added: llvm/trunk/test/CodeGen/X86/loop-strength-reduce7.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/loop-strength-reduce7.ll?rev=65178&view=auto
>
> = 
> = 
> = 
> = 
> = 
> = 
> = 
> = 
> ======================================================================
> --- llvm/trunk/test/CodeGen/X86/loop-strength-reduce7.ll (added)
> +++ llvm/trunk/test/CodeGen/X86/loop-strength-reduce7.ll Fri Feb 20  
> 16:16:49 2009
> @@ -0,0 +1,44 @@
> +; RUN: llvm-as < %s | llc -march=x86 | not grep imul
> +
> +target triple = "i386-apple-darwin9.6"
> +	%struct.III_psy_xmin = type { [22 x double], [13 x [3 x double]] }
> +	%struct.III_scalefac_t = type { [22 x i32], [13 x [3 x i32]] }
> +	%struct.gr_info = type { i32, i32, i32, i32, i32, i32, i32, i32,  
> [3 x i32], [3 x i32], i32, i32, i32, i32, i32, i32, i32, i32, i32,  
> i32*, [4 x i32] }
> +	%struct.lame_global_flags = type { i32, i32, i32, i32, i32, i32,  
> i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32,  
> i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i8*,  
> i8*, i32, i32, float, i32, i32, i32, i32, i32, i32, i32, i32, i32,  
> i32, i32, i32, i32, float, i32, i32, i32, float, float, float,  
> float, i32, i32, i32, i32, i32, i32, i32, i32 }
> +
> +define fastcc void @outer_loop(%struct.lame_global_flags* nocapture  
> %gfp, double* nocapture %xr, i32 %targ_bits, double* nocapture  
> %best_noise, %struct.III_psy_xmin* nocapture %l3_xmin, i32*  
> nocapture %l3_enc, %struct.III_scalefac_t* nocapture %scalefac,  
> %struct.gr_info* nocapture %cod_info, i32 %ch) nounwind {
> +entry:
> +	br label %bb4
> +
> +bb4:		; preds = %bb4, %entry
> +	br i1 true, label %bb5, label %bb4
> +
> +bb5:		; preds = %bb4
> +	br i1 true, label %bb28.i37, label %bb.i4
> +
> +bb.i4:		; preds = %bb.i4, %bb5
> +	br label %bb.i4
> +
> +bb28.i37:		; preds = %bb33.i47, %bb5
> +	%i.1.reg2mem.0.i = phi i32 [ %0, %bb33.i47 ], [ 0, %bb5 ]		; <i32>  
> [#uses=2]
> +	%0 = add i32 %i.1.reg2mem.0.i, 1		; <i32> [#uses=2]
> +	br label %bb29.i38
> +
> +bb29.i38:		; preds = %bb33.i47, %bb28.i37
> +	%indvar32.i = phi i32 [ %indvar.next33.i, %bb33.i47 ], [ 0,  
> %bb28.i37 ]		; <i32> [#uses=2]
> +	%sfb.314.i = add i32 %indvar32.i, 0		; <i32> [#uses=3]
> +	%1 = getelementptr [4 x [21 x double]]* null, i32 0, i32 %0, i32  
> %sfb.314.i		; <double*> [#uses=1]
> +	%2 = load double* %1, align 8		; <double> [#uses=0]
> +	br i1 false, label %bb30.i41, label %bb33.i47
> +
> +bb30.i41:		; preds = %bb29.i38
> +	%3 = getelementptr %struct.III_scalefac_t* null, i32 0, i32 1, i32  
> %sfb.314.i, i32 %i.1.reg2mem.0.i		; <i32*> [#uses=1]
> +	store i32 0, i32* %3, align 4
> +	br label %bb33.i47
> +
> +bb33.i47:		; preds = %bb30.i41, %bb29.i38
> +	%4 = add i32 %sfb.314.i, 1		; <i32> [#uses=1]
> +	%phitmp.i46 = icmp ugt i32 %4, 11		; <i1> [#uses=1]
> +	%indvar.next33.i = add i32 %indvar32.i, 1		; <i32> [#uses=1]
> +	br i1 %phitmp.i46, label %bb28.i37, label %bb29.i38
> +}
>
>
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