[CVP] Deduce no-wrap on `mul`

[lebedev.ri]

Summary

ConstantRange::makeGuaranteedNoWrapRegion() knows how to deal with mul
since rL335646, there is exhaustive test coverage.
This is already used by CVP's processOverflowIntrinsic(),
and by SCEV's StrengthenNoWrapFlags()

That being said, currently, this doesn't help much in the end:

statistic	old	new	delta	percentage
correlated-value-propagation.NumMulNSW	4	275	271	6775.00%
correlated-value-propagation.NumMulNUW	4	1323	1319	32975.00%
correlated-value-propagation.NumMulNW	8	1598	1590	19875.00%
correlated-value-propagation.NumNSW	5715	5986	271	4.74%
correlated-value-propagation.NumNUW	9193	10512	1319	14.35%
correlated-value-propagation.NumNW	14908	16498	1590	10.67%
instcount.NumAddInst	275871	275869	-2	0.00%
instcount.NumBrInst	708234	708232	-2	0.00%
instcount.NumMulInst	43812	43810	-2	0.00%
instcount.NumPHIInst	316786	316784	-2	0.00%
instcount.NumTruncInst	62165	62167	2	0.00%
instcount.NumUDivInst	2528	2526	-2	-0.08%
instcount.TotalBlocks	842995	842993	-2	0.00%
instcount.TotalInsts	7376486	7376478	-8	0.00%

(^ test-suite plain, tests still pass)

Do we want this for consistency?

[reames]

LGTM

[lebedev.ri]

In D69203#1716080, @reames wrote:

LGTM

Okay, thank you for the review.
shl to follow.

llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp

for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE;) {
       case Instruction::AShr:
         BBChanged |= processAShr(cast<BinaryOperator>(II), LVI);
         break;
       case Instruction::SExt:
         BBChanged |= processSExt(cast<SExtInst>(II), LVI);
         break;
       case Instruction::Add:
       case Instruction::Sub:
+      case Instruction::Mul:
         BBChanged |= processBinOp(cast<BinaryOperator>(II), LVI);
         break;
       case Instruction::And:
         BBChanged |= processAnd(cast<BinaryOperator>(II), LVI);
         break;
       }
     }
 

llvm/test/Transforms/CorrelatedValuePropagation/mul.ll

 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
 ; RUN: opt < %s -correlated-propagation -cvp-dont-add-nowrap-flags=false -S | FileCheck %s
 
 define i8 @test0(i8 %a) {
 ; CHECK-LABEL: @test0(
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[CMP:%.*]] = icmp ult i8 [[A:%.*]], 3
 ; CHECK-NEXT:    br i1 [[CMP]], label [[BB:%.*]], label [[EXIT:%.*]]
 ; CHECK:       bb:
-; CHECK-NEXT:    [[MUL:%.*]] = mul i8 [[A]], 50
+; CHECK-NEXT:    [[MUL:%.*]] = mul nuw nsw i8 [[A]], 50
 ; CHECK-NEXT:    ret i8 [[MUL]]
 ; CHECK:       exit:
 ; CHECK-NEXT:    ret i8 0
 ;
 entry:
   %cmp = icmp ult i8 %a, 3
   br i1 %cmp, label %bb, label %exit
 
 bb:
   %mul = mul i8 %a, 50
   ret i8 %mul
 
 exit:
   ret i8 0
 }
 
 define i8 @test1(i8 %a) {
 ; CHECK-LABEL: @test1(
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[CMP:%.*]] = icmp ult i8 [[A:%.*]], 4
 ; CHECK-NEXT:    br i1 [[CMP]], label [[BB:%.*]], label [[EXIT:%.*]]
 ; CHECK:       bb:
-; CHECK-NEXT:    [[MUL:%.*]] = mul i8 [[A]], 50
+; CHECK-NEXT:    [[MUL:%.*]] = mul nuw i8 [[A]], 50
 ; CHECK-NEXT:    ret i8 [[MUL]]
 ; CHECK:       exit:
 ; CHECK-NEXT:    ret i8 0
 ;
 entry:
   %cmp = icmp ult i8 %a, 4
   br i1 %cmp, label %bb, label %exit
 
 bb:
   %mul = mul i8 %a, 50
   ret i8 %mul
 
 exit:
   ret i8 0
 }
 
 define i8 @test2(i8 %a) {
 ; CHECK-LABEL: @test2(
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[CMP:%.*]] = icmp ult i8 [[A:%.*]], 6
 ; CHECK-NEXT:    br i1 [[CMP]], label [[BB:%.*]], label [[EXIT:%.*]]
 ; CHECK:       bb:
-; CHECK-NEXT:    [[MUL:%.*]] = mul i8 [[A]], 50
+; CHECK-NEXT:    [[MUL:%.*]] = mul nuw i8 [[A]], 50
 ; CHECK-NEXT:    ret i8 [[MUL]]
 ; CHECK:       exit:
 ; CHECK-NEXT:    ret i8 0
 ;
 entry:
   %cmp = icmp ult i8 %a, 6
   br i1 %cmp, label %bb, label %exit
 

 define i8 @test4(i8 %a) {
 ; CHECK-LABEL: @test4(
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[CMP1:%.*]] = icmp slt i8 [[A:%.*]], 3
 ; CHECK-NEXT:    [[CMP2:%.*]] = icmp sgt i8 [[A]], -3
 ; CHECK-NEXT:    [[COND:%.*]] = and i1 [[CMP1]], [[CMP2]]
 ; CHECK-NEXT:    br i1 [[COND]], label [[BB:%.*]], label [[EXIT:%.*]]
 ; CHECK:       bb:
-; CHECK-NEXT:    [[MUL:%.*]] = mul i8 [[A]], 50
+; CHECK-NEXT:    [[MUL:%.*]] = mul nsw i8 [[A]], 50
 ; CHECK-NEXT:    ret i8 [[MUL]]
 ; CHECK:       exit:
 ; CHECK-NEXT:    ret i8 0
 ;
 entry:
   %cmp1 = icmp slt i8 %a, 3
   %cmp2 = icmp sgt i8 %a, -3
   %cond = and i1 %cmp1, %cmp2