[PATCH] D68654: [CVP} Replace SExt with ZExt if the input is known-non-negative

[Roman Lebedev via Phabricator via llvm-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rG354ba6985ca0: [CVP} Replace SExt with ZExt if the input is known-non-negative (authored by lebedev.ri).

Changed prior to commit:
  https://reviews.llvm.org/D68654?vs=223904&id=223933#toc

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D68654/new/

https://reviews.llvm.org/D68654

Files:
  llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
  llvm/test/Transforms/CorrelatedValuePropagation/sext.ll


Index: llvm/test/Transforms/CorrelatedValuePropagation/sext.ll
===================================================================
--- llvm/test/Transforms/CorrelatedValuePropagation/sext.ll
+++ llvm/test/Transforms/CorrelatedValuePropagation/sext.ll
@@ -18,9 +18,9 @@
 ; CHECK-NEXT:    [[CMP:%.*]] = icmp sgt i32 [[A]], -1
 ; CHECK-NEXT:    br i1 [[CMP]], label [[FOR_BODY]], label [[FOR_END:%.*]]
 ; CHECK:       for.body:
-; CHECK-NEXT:    [[EXT_WIDE:%.*]] = sext i32 [[A]] to i64
-; CHECK-NEXT:    call void @use64(i64 [[EXT_WIDE]])
-; CHECK-NEXT:    [[EXT]] = trunc i64 [[EXT_WIDE]] to i32
+; CHECK-NEXT:    [[EXT_WIDE1:%.*]] = zext i32 [[A]] to i64
+; CHECK-NEXT:    call void @use64(i64 [[EXT_WIDE1]])
+; CHECK-NEXT:    [[EXT]] = trunc i64 [[EXT_WIDE1]] to i32
 ; CHECK-NEXT:    br label [[FOR_COND]]
 ; CHECK:       for.end:
 ; CHECK-NEXT:    ret void
@@ -85,9 +85,9 @@
 ; CHECK-NEXT:    [[CMP:%.*]] = icmp sgt i32 [[N:%.*]], -1
 ; CHECK-NEXT:    br i1 [[CMP]], label [[BB:%.*]], label [[EXIT:%.*]]
 ; CHECK:       bb:
-; CHECK-NEXT:    [[EXT_WIDE:%.*]] = sext i32 [[N]] to i64
-; CHECK-NEXT:    call void @use64(i64 [[EXT_WIDE]])
-; CHECK-NEXT:    [[EXT:%.*]] = trunc i64 [[EXT_WIDE]] to i32
+; CHECK-NEXT:    [[EXT_WIDE1:%.*]] = zext i32 [[N]] to i64
+; CHECK-NEXT:    call void @use64(i64 [[EXT_WIDE1]])
+; CHECK-NEXT:    [[EXT:%.*]] = trunc i64 [[EXT_WIDE1]] to i32
 ; CHECK-NEXT:    br label [[EXIT]]
 ; CHECK:       exit:
 ; CHECK-NEXT:    ret void
Index: llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
+++ llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
@@ -62,6 +62,7 @@
 STATISTIC(NumUDivs,     "Number of udivs whose width was decreased");
 STATISTIC(NumAShrs,     "Number of ashr converted to lshr");
 STATISTIC(NumSRems,     "Number of srem converted to urem");
+STATISTIC(NumSExt,      "Number of sext converted to zext");
 STATISTIC(NumOverflows, "Number of overflow checks removed");
 STATISTIC(NumSaturating,
     "Number of saturating arithmetics converted to normal arithmetics");
@@ -637,6 +638,27 @@
   return true;
 }
 
+static bool processSExt(SExtInst *SDI, LazyValueInfo *LVI) {
+  if (SDI->getType()->isVectorTy())
+    return false;
+
+  Value *Base = SDI->getOperand(0);
+
+  Constant *Zero = ConstantInt::get(Base->getType(), 0);
+  if (LVI->getPredicateAt(ICmpInst::ICMP_SGE, Base, Zero, SDI) !=
+      LazyValueInfo::True)
+    return false;
+
+  ++NumSExt;
+  auto *ZExt =
+      CastInst::CreateZExtOrBitCast(Base, SDI->getType(), SDI->getName(), SDI);
+  ZExt->setDebugLoc(SDI->getDebugLoc());
+  SDI->replaceAllUsesWith(ZExt);
+  SDI->eraseFromParent();
+
+  return true;
+}
+
 static bool processBinOp(BinaryOperator *BinOp, LazyValueInfo *LVI) {
   using OBO = OverflowingBinaryOperator;
 
@@ -745,6 +767,9 @@
       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:
         BBChanged |= processBinOp(cast<BinaryOperator>(II), LVI);


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