[llvm-commits] [llvm] r123105 - in /llvm/trunk: lib/Analysis/ScalarEvolution.cpp test/Analysis/ScalarEvolution/nsw.ll

[Nick Lewycky]

Chris Lattner wrote:
> Author: lattner
> Date: Sat Jan  8 20:28:48 2011
> New Revision: 123105
>
> URL: http://llvm.org/viewvc/llvm-project?rev=123105&view=rev
> Log:
> teach SCEV analysis of PHI nodes that PHI recurences formed
> with GEP instructions are always NUW, because PHIs cannot wrap
> the end of the address space.

Aren't GEPs also NSW? I tried looking this up in the LangRef but wasn't 
able to find it, but I've been coding under the impression that GEPs are 
both nuw and nsw.

Nick

>
> Modified:
>      llvm/trunk/lib/Analysis/ScalarEvolution.cpp
>      llvm/trunk/test/Analysis/ScalarEvolution/nsw.ll
>
> Modified: llvm/trunk/lib/Analysis/ScalarEvolution.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ScalarEvolution.cpp?rev=123105&r1=123104&r2=123105&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Analysis/ScalarEvolution.cpp (original)
> +++ llvm/trunk/lib/Analysis/ScalarEvolution.cpp Sat Jan  8 20:28:48 2011
> @@ -2719,6 +2719,11 @@
>                     HasNUW = true;
>                   if (OBO->hasNoSignedWrap())
>                     HasNSW = true;
> +              } else if (isa<GEPOperator>(BEValueV)) {
> +                // If the increment is a GEP, then we know it won't perform an
> +                // unsigned overflow, because the address space cannot be
> +                // wrapped around.
> +                HasNUW = true;
>                 }
>
>                 const SCEV *StartVal = getSCEV(StartValueV);
>
> Modified: llvm/trunk/test/Analysis/ScalarEvolution/nsw.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Analysis/ScalarEvolution/nsw.ll?rev=123105&r1=123104&r2=123105&view=diff
> ==============================================================================
> --- llvm/trunk/test/Analysis/ScalarEvolution/nsw.ll (original)
> +++ llvm/trunk/test/Analysis/ScalarEvolution/nsw.ll Sat Jan  8 20:28:48 2011
> @@ -1,10 +1,11 @@
> -; RUN: opt<  %s -analyze -scalar-evolution | grep { -->   {.*,+,.*}.*<%bb>} | count 8
> +; RUN: opt<  %s -analyze -scalar-evolution | FileCheck %s
>
>   ; The addrecs in this loop are analyzable only by using nsw information.
>
>   target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64"
>
> -define void @foo(double* %p) nounwind {
> +; CHECK: Classifying expressions for: @test1
> +define void @test1(double* %p) nounwind {
>   entry:
>   	%tmp = load double* %p, align 8		;<double>  [#uses=1]
>   	%tmp1 = fcmp ogt double %tmp, 2.000000e+00		;<i1>  [#uses=1]
> @@ -15,19 +16,29 @@
>
>   bb:		; preds = %bb1, %bb.nph
>   	%i.01 = phi i32 [ %tmp8, %bb1 ], [ 0, %bb.nph ]		;<i32>  [#uses=3]
> +; CHECK: %i.01
> +; CHECK-NEXT: -->   {0,+,1}<nuw><nsw><%bb>
>   	%tmp2 = sext i32 %i.01 to i64		;<i64>  [#uses=1]
>   	%tmp3 = getelementptr double* %p, i64 %tmp2		;<double*>  [#uses=1]
>   	%tmp4 = load double* %tmp3, align 8		;<double>  [#uses=1]
>   	%tmp5 = fmul double %tmp4, 9.200000e+00		;<double>  [#uses=1]
>   	%tmp6 = sext i32 %i.01 to i64		;<i64>  [#uses=1]
>   	%tmp7 = getelementptr double* %p, i64 %tmp6		;<double*>  [#uses=1]
> +; CHECK: %tmp7
> +; CHECK-NEXT:   -->   {%p,+,8}<%bb>
>   	store double %tmp5, double* %tmp7, align 8
>   	%tmp8 = add nsw i32 %i.01, 1		;<i32>  [#uses=2]
> +; CHECK: %tmp8
> +; CHECK-NEXT: -->   {1,+,1}<nuw><nsw><%bb>
>   	br label %bb1
>
>   bb1:		; preds = %bb
>   	%phitmp = sext i32 %tmp8 to i64		;<i64>  [#uses=1]
> +; CHECK: %phitmp
> +; CHECK-NEXT: -->   {1,+,1}<%bb>
>   	%tmp9 = getelementptr double* %p, i64 %phitmp		;<double*>  [#uses=1]
> +; CHECK: %tmp9
> +; CHECK-NEXT:  -->   {(8 + %p),+,8}<%bb>
>   	%tmp10 = load double* %tmp9, align 8		;<double>  [#uses=1]
>   	%tmp11 = fcmp ogt double %tmp10, 2.000000e+00		;<i1>  [#uses=1]
>   	br i1 %tmp11, label %bb, label %bb1.return_crit_edge
> @@ -38,3 +49,30 @@
>   return:		; preds = %bb1.return_crit_edge, %entry
>   	ret void
>   }
> +
> +; CHECK: Classifying expressions for: @test2
> +define void @test2(i32* %begin, i32* %end) ssp {
> +entry:
> +  %cmp1.i.i = icmp eq i32* %begin, %end
> +  br i1 %cmp1.i.i, label %_ZSt4fillIPiiEvT_S1_RKT0_.exit, label %for.body.lr.ph.i.i
> +
> +for.body.lr.ph.i.i:                               ; preds = %entry
> +  br label %for.body.i.i
> +
> +for.body.i.i:                                     ; preds = %for.body.i.i, %for.body.lr.ph.i.i
> +  %__first.addr.02.i.i = phi i32* [ %begin, %for.body.lr.ph.i.i ], [ %ptrincdec.i.i, %for.body.i.i ]
> +; CHECK: %__first.addr.02.i.i
> +; CHECK-NEXT: -->   {%begin,+,4}<nuw><%for.body.i.i>	
> +  store i32 0, i32* %__first.addr.02.i.i, align 4
> +  %ptrincdec.i.i = getelementptr inbounds i32* %__first.addr.02.i.i, i64 1
> +; CHECK: %ptrincdec.i.i
> +; CHECK-NEXT: -->   {(4 + %begin),+,4}<nuw><%for.body.i.i>
> +  %cmp.i.i = icmp eq i32* %ptrincdec.i.i, %end
> +  br i1 %cmp.i.i, label %for.cond.for.end_crit_edge.i.i, label %for.body.i.i
> +
> +for.cond.for.end_crit_edge.i.i:                   ; preds = %for.body.i.i
> +  br label %_ZSt4fillIPiiEvT_S1_RKT0_.exit
> +
> +_ZSt4fillIPiiEvT_S1_RKT0_.exit:                   ; preds = %entry, %for.cond.for.end_crit_edge.i.i
> +  ret void
> +}
>
>
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