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Author SHA1 Message Date
Sanjoy Das 7c0ce26614 This patch teaches IndVarSimplify to add nuw and nsw to certain kinds 
of operations that provably don't overflow. For example, we can prove
%civ.inc below does not sign-overflow. With this change,
IndVarSimplify changes %civ.inc to an add nsw.

  define i32 @foo(i32* %array, i32* %length_ptr, i32 %init) {
   entry:
    %length = load i32* %length_ptr, !range !0
    %len.sub.1 = sub i32 %length, 1
    %upper = icmp slt i32 %init, %len.sub.1
    br i1 %upper, label %loop, label %exit
  
   loop:
    %civ = phi i32 [ %init, %entry ], [ %civ.inc, %latch ]
    %civ.inc = add i32 %civ, 1
    %cmp = icmp slt i32 %civ.inc, %length
    br i1 %cmp, label %latch, label %break
  
   latch:
    store i32 0, i32* %array
    %check = icmp slt i32 %civ.inc, %len.sub.1
    br i1 %check, label %loop, label %break
  
   break:
    ret i32 %civ.inc
  
   exit:
    ret i32 42
  }

Differential Revision: http://reviews.llvm.org/D6748

llvm-svn: 225282
 2015-01-06 19:02:56 +00:00
Zinovy Nis ccc3e3733b [BUG][INDVAR] Fix for PR21014: wrong SCEV operands commuting for non-commutative instructions 
My commit rL216160 introduced a bug PR21014: IndVars widens code 'for (i = ; i < ...; i++) arr[ CONST - i]' into 'for (i = ; i < ...; i++) arr[ i - CONST]'
thus inverting index expression. This patch fixes it. 
Thanks to Jörg Sonnenberger for pointing.

Differential Revision: http://reviews.llvm.org/D5576

llvm-svn: 218867
 2014-10-02 13:01:15 +00:00
Zinovy Nis 0a36cba29d [INDVARS] Extend using of widening of induction variables for the cases of "sub nsw" and "mul nsw" instructions. 
Currently only "add nsw" are widened. This patch eliminates tons of "sext" instructions for 64 bit code (and the corresponding target code) in cases like:

int N = 100;
float **A;

void foo(int x0, int x1)
{
        float * A_cur = &A[0][0];
        float * A_next = &A[1][0];
        for(int x = x0; x < x1; ++x).
        {
          // Currently only [x+N] case is widened. Others 2 cases lead to sext.
          // This patch fixes it, so all 3 cases do not need sext.
          const float div = A_cur[x + N] + A_cur[x - N] + A_cur[x * N];
          A_next[x] = div;
        }
}
...
> clang++ test.cpp -march=core-avx2 -Ofast  -fno-unroll-loops -fno-tree-vectorize -S -o -

Differential Revision: http://reviews.llvm.org/D4695

llvm-svn: 216160
 2014-08-21 08:25:45 +00:00
Andrew Trick db149f9e73 Remove redundant -enable-iv-rewrite=false flags from test cases. 
llvm-svn: 153255
 2012-03-22 17:09:04 +00:00
Andrew Trick e756031a62 Reenable this IndVars unit test. 
SCEV can't optimize undef in all cases, which is a separate issue from this test case.

llvm-svn: 145343
 2011-11-29 00:52:04 +00:00
Benjamin Kramer 650c09aa4d XFAIL this test until I figure out what indvars is doing here (or find someone who does) 
llvm-svn: 145008
 2011-11-20 11:10:03 +00:00
Andrew Trick 183013d8d4 Rename -disable-iv-rewrite to -enable-iv-rewrite=false in preparation for default change. 
llvm-svn: 139517
 2011-09-12 18:28:44 +00:00
Andrew Trick 8c6fb3af6e Test case for r139453, WidenIV::GetExtendedOperandRecurrence. 
llvm-svn: 139504
 2011-09-12 17:20:57 +00:00