[llvm] 2c16100 - [ScalarEvolution] createSCEV(): recognize `udiv`/`urem` disguised as an `sdiv`/`srem`
Roman Lebedev via llvm-commits
llvm-commits at lists.llvm.org
Thu Jul 2 03:22:52 PDT 2020
Author: Roman Lebedev
Date: 2020-07-02T13:22:12+03:00
New Revision: 2c16100e6f72075564ea1f67fa5a82c269dafcd3
URL: https://github.com/llvm/llvm-project/commit/2c16100e6f72075564ea1f67fa5a82c269dafcd3
DIFF: https://github.com/llvm/llvm-project/commit/2c16100e6f72075564ea1f67fa5a82c269dafcd3.diff
LOG: [ScalarEvolution] createSCEV(): recognize `udiv`/`urem` disguised as an `sdiv`/`srem`
Summary:
While InstCombine trivially converts that `srem` into a `urem`,
it might happen later than wanted, in particular i'd like
for that to happen on https://godbolt.org/z/bwuEmJ test case
early in pipeline, before first instcombine run, just before `-mem2reg`.
SCEV should recognize this case natively.
Reviewers: mkazantsev, efriedma, nikic, reames
Reviewed By: efriedma
Subscribers: clementval, hiraditya, javed.absar, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D82721
Added:
Modified:
llvm/lib/Analysis/ScalarEvolution.cpp
llvm/test/Analysis/ScalarEvolution/sdiv.ll
llvm/test/Analysis/ScalarEvolution/srem.ll
Removed:
################################################################################
diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp
index 609ad639d9c0..75926aa3a960 100644
--- a/llvm/lib/Analysis/ScalarEvolution.cpp
+++ b/llvm/lib/Analysis/ScalarEvolution.cpp
@@ -6303,6 +6303,20 @@ const SCEV *ScalarEvolution::createSCEV(Value *V) {
return getSCEV(U->getOperand(0));
break;
+ case Instruction::SDiv:
+ // If both operands are non-negative, this is just an udiv.
+ if (isKnownNonNegative(getSCEV(U->getOperand(0))) &&
+ isKnownNonNegative(getSCEV(U->getOperand(1))))
+ return getUDivExpr(getSCEV(U->getOperand(0)), getSCEV(U->getOperand(1)));
+ break;
+
+ case Instruction::SRem:
+ // If both operands are non-negative, this is just an urem.
+ if (isKnownNonNegative(getSCEV(U->getOperand(0))) &&
+ isKnownNonNegative(getSCEV(U->getOperand(1))))
+ return getURemExpr(getSCEV(U->getOperand(0)), getSCEV(U->getOperand(1)));
+ break;
+
// It's tempting to handle inttoptr and ptrtoint as no-ops, however this can
// lead to pointer expressions which cannot safely be expanded to GEPs,
// because ScalarEvolution doesn't respect the GEP aliasing rules when
diff --git a/llvm/test/Analysis/ScalarEvolution/sdiv.ll b/llvm/test/Analysis/ScalarEvolution/sdiv.ll
index b4895855ab71..106cda1b7f0f 100644
--- a/llvm/test/Analysis/ScalarEvolution/sdiv.ll
+++ b/llvm/test/Analysis/ScalarEvolution/sdiv.ll
@@ -14,11 +14,11 @@ define dso_local void @_Z4loopi(i32 %width) local_unnamed_addr #0 {
; CHECK-NEXT: %i.0 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
; CHECK-NEXT: --> {0,+,1}<nuw><nsw><%for.cond> U: [0,-2147483648) S: [0,-2147483648) Exits: %width LoopDispositions: { %for.cond: Computable }
; CHECK-NEXT: %rem = sdiv i32 %i.0, 2
-; CHECK-NEXT: --> %rem U: full-set S: [-1073741824,1073741824) Exits: <<Unknown>> LoopDispositions: { %for.cond: Variant }
+; CHECK-NEXT: --> ({0,+,1}<nuw><nsw><%for.cond> /u 2) U: [0,1073741824) S: [0,1073741824) Exits: (%width /u 2) LoopDispositions: { %for.cond: Computable }
; CHECK-NEXT: %idxprom = sext i32 %rem to i64
-; CHECK-NEXT: --> (sext i32 %rem to i64) U: [-2147483648,2147483648) S: [-1073741824,1073741824) Exits: <<Unknown>> LoopDispositions: { %for.cond: Variant }
+; CHECK-NEXT: --> ({0,+,1}<nuw><nsw><%for.cond> /u 2) U: [0,2147483648) S: [0,2147483648) Exits: ((zext i32 %width to i64) /u 2) LoopDispositions: { %for.cond: Computable }
; CHECK-NEXT: %arrayidx = getelementptr inbounds [2 x i32], [2 x i32]* %storage, i64 0, i64 %idxprom
-; CHECK-NEXT: --> ((4 * (sext i32 %rem to i64))<nsw> + %storage)<nsw> U: [0,-3) S: [-9223372036854775808,9223372036854775805) Exits: <<Unknown>> LoopDispositions: { %for.cond: Variant }
+; CHECK-NEXT: --> ((4 * ({0,+,1}<nuw><nsw><%for.cond> /u 2))<nuw><nsw> + %storage)<nsw> U: [0,-3) S: [-9223372036854775808,9223372036854775805) Exits: ((4 * ((zext i32 %width to i64) /u 2))<nuw><nsw> + %storage)<nsw> LoopDispositions: { %for.cond: Computable }
; CHECK-NEXT: %1 = load i32, i32* %arrayidx, align 4
; CHECK-NEXT: --> %1 U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %for.cond: Variant }
; CHECK-NEXT: %call = call i32 @_Z3adji(i32 %1)
diff --git a/llvm/test/Analysis/ScalarEvolution/srem.ll b/llvm/test/Analysis/ScalarEvolution/srem.ll
index 365b40d88e24..6debab34e3b3 100644
--- a/llvm/test/Analysis/ScalarEvolution/srem.ll
+++ b/llvm/test/Analysis/ScalarEvolution/srem.ll
@@ -14,11 +14,11 @@ define dso_local void @_Z4loopi(i32 %width) local_unnamed_addr #0 {
; CHECK-NEXT: %i.0 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
; CHECK-NEXT: --> {0,+,1}<nuw><nsw><%for.cond> U: [0,-2147483648) S: [0,-2147483648) Exits: %width LoopDispositions: { %for.cond: Computable }
; CHECK-NEXT: %rem = srem i32 %i.0, 2
-; CHECK-NEXT: --> %rem U: [0,2) S: [-2,2) Exits: <<Unknown>> LoopDispositions: { %for.cond: Variant }
+; CHECK-NEXT: --> (zext i1 {false,+,true}<%for.cond> to i32) U: [0,2) S: [0,2) Exits: (zext i1 (trunc i32 %width to i1) to i32) LoopDispositions: { %for.cond: Computable }
; CHECK-NEXT: %idxprom = sext i32 %rem to i64
-; CHECK-NEXT: --> (sext i32 %rem to i64) U: [0,2) S: [-2,2) Exits: <<Unknown>> LoopDispositions: { %for.cond: Variant }
+; CHECK-NEXT: --> (zext i1 {false,+,true}<%for.cond> to i64) U: [0,2) S: [0,2) Exits: (zext i1 (trunc i32 %width to i1) to i64) LoopDispositions: { %for.cond: Computable }
; CHECK-NEXT: %arrayidx = getelementptr inbounds [2 x i32], [2 x i32]* %storage, i64 0, i64 %idxprom
-; CHECK-NEXT: --> ((4 * (sext i32 %rem to i64))<nuw><nsw> + %storage)<nsw> U: [0,-3) S: [-9223372036854775808,9223372036854775805) Exits: <<Unknown>> LoopDispositions: { %for.cond: Variant }
+; CHECK-NEXT: --> ((4 * (zext i1 {false,+,true}<%for.cond> to i64))<nuw><nsw> + %storage)<nsw> U: [0,-3) S: [-9223372036854775808,9223372036854775805) Exits: ((4 * (zext i1 (trunc i32 %width to i1) to i64))<nuw><nsw> + %storage)<nsw> LoopDispositions: { %for.cond: Computable }
; CHECK-NEXT: %1 = load i32, i32* %arrayidx, align 4
; CHECK-NEXT: --> %1 U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %for.cond: Variant }
; CHECK-NEXT: %call = call i32 @_Z3adji(i32 %1)
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