[PATCH] D69942: [ConstantRange][LVI] Use overflow flags from `sub` to constrain the range

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri created this revision.
lebedev.ri added reviewers: nikic, reames, spatel.
lebedev.ri added a project: LLVM.
Herald added a subscriber: hiraditya.

This notably improves non-negativity deduction:

  | statistic                              |     old |     new | delta | % change |
  | correlated-value-propagation.NumAShrs  |     209 |     227 |    18 |  8.6124% |
  | correlated-value-propagation.NumAddNSW |    4972 |    4988 |    16 |  0.3218% |
  | correlated-value-propagation.NumAddNUW |    7141 |    7148 |     7 |  0.0980% |
  | correlated-value-propagation.NumAddNW  |   12113 |   12136 |    23 |  0.1899% |
  | correlated-value-propagation.NumAnd    |     442 |     445 |     3 |  0.6787% |
  | correlated-value-propagation.NumNSW    |    7160 |    7176 |    16 |  0.2235% |
  | correlated-value-propagation.NumNUW    |   13306 |   13316 |    10 |  0.0752% |
  | correlated-value-propagation.NumNW     |   20466 |   20492 |    26 |  0.1270% |
  | correlated-value-propagation.NumSDivs  |     207 |     212 |     5 |  2.4155% |
  | correlated-value-propagation.NumSExt   |    6279 |    6679 |   400 |  6.3704% |
  | correlated-value-propagation.NumSRems  |      28 |      29 |     1 |  3.5714% |
  | correlated-value-propagation.NumShlNUW |    2793 |    2796 |     3 |  0.1074% |
  | correlated-value-propagation.NumShlNW  |    3964 |    3967 |     3 |  0.0757% |
  | correlated-value-propagation.NumUDivs  |     353 |     358 |     5 |  1.4164% |
  | instcount.NumAShrInst                  |   13763 |   13741 |   -22 | -0.1598% |
  | instcount.NumAddInst                   |  277349 |  277348 |    -1 | -0.0004% |
  | instcount.NumLShrInst                  |   27437 |   27463 |    26 |  0.0948% |
  | instcount.NumOrInst                    |  102677 |  102678 |     1 |  0.0010% |
  | instcount.NumSDivInst                  |    8732 |    8727 |    -5 | -0.0573% |
  | instcount.NumSExtInst                  |   80872 |   80468 |  -404 | -0.4996% |
  | instcount.NumSRemInst                  |    1679 |    1678 |    -1 | -0.0596% |
  | instcount.NumTruncInst                 |   62154 |   62153 |    -1 | -0.0016% |
  | instcount.NumUDivInst                  |    2526 |    2527 |     1 |  0.0396% |
  | instcount.NumURemInst                  |    1589 |    1590 |     1 |  0.0629% |
  | instcount.NumZExtInst                  |   69405 |   69809 |   404 |  0.5821% |
  | instcount.TotalInsts                   | 7439575 | 7439574 |    -1 |  0.0000% |


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D69942

Files:
  llvm/lib/IR/ConstantRange.cpp
  llvm/test/Transforms/CorrelatedValuePropagation/icmp.ll


Index: llvm/test/Transforms/CorrelatedValuePropagation/icmp.ll
===================================================================
--- llvm/test/Transforms/CorrelatedValuePropagation/icmp.ll
+++ llvm/test/Transforms/CorrelatedValuePropagation/icmp.ll
@@ -490,11 +490,9 @@
 ; CHECK-NEXT:    [[SUB:%.*]] = sub nuw nsw i32 [[A]], [[B]]
 ; CHECK-NEXT:    br label [[CONT:%.*]]
 ; CHECK:       cont:
-; CHECK-NEXT:    [[RES:%.*]] = icmp sge i32 [[SUB]], 0
 ; CHECK-NEXT:    br label [[EXIT]]
 ; CHECK:       exit:
-; CHECK-NEXT:    [[IV:%.*]] = phi i1 [ true, [[BEGIN:%.*]] ], [ [[RES]], [[CONT]] ]
-; CHECK-NEXT:    ret i1 [[IV]]
+; CHECK-NEXT:    ret i1 true
 ;
 begin:
   %cmp0 = icmp sge i32 %a, 0
@@ -598,11 +596,9 @@
 ; CHECK-NEXT:    [[SUB:%.*]] = sub nsw i32 [[A]], [[B]]
 ; CHECK-NEXT:    br label [[CONT:%.*]]
 ; CHECK:       cont:
-; CHECK-NEXT:    [[RES:%.*]] = icmp sle i32 [[SUB]], 0
 ; CHECK-NEXT:    br label [[EXIT]]
 ; CHECK:       exit:
-; CHECK-NEXT:    [[IV:%.*]] = phi i1 [ true, [[BEGIN:%.*]] ], [ [[RES]], [[CONT]] ]
-; CHECK-NEXT:    ret i1 [[IV]]
+; CHECK-NEXT:    ret i1 true
 ;
 begin:
   %cmp0 = icmp sle i32 %a, 0
Index: llvm/lib/IR/ConstantRange.cpp
===================================================================
--- llvm/lib/IR/ConstantRange.cpp
+++ llvm/lib/IR/ConstantRange.cpp
@@ -824,6 +824,8 @@
   switch (BinOp) {
   case Instruction::Add:
     return addWithNoWrap(Other, NoWrapKind);
+  case Instruction::Sub:
+    return subWithNoWrap(Other, NoWrapKind);
   default:
     // Don't know about this Overflowing Binary Operation.
     // Conservatively fallback to plain binop handling.


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