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[SCEV] Support larger than 64-bit types in ashr(add(shl(x, n), c), m) #71600

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Merged
merged 1 commit into from
Nov 8, 2023
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[SCEV] Support larger than 64-bit types in ashr(add(shl(x, n), c), m) #71600

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3 changes: 1 addition & 2 deletions llvm/lib/Analysis/ScalarEvolution.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -7888,8 +7888,7 @@ const SCEV *ScalarEvolution::createSCEV(Value *V) {
// same type, so create a new Constant with type same as TruncTy.
// Also, the Add constant should be shifted right by AShr amount.
APInt AddOperand = AddOperandCI->getValue().ashr(AShrAmt);
AddConstant = getConstant(TruncTy, AddOperand.getZExtValue(),
AddOperand.isSignBitSet());
AddConstant = getConstant(AddOperand.trunc(BitWidth - AShrAmt));
// we model the expression as sext(add(trunc(A), c << n)), since the
// sext(trunc) part is already handled below, we create a
// AddExpr(TruncExp) which will be used later.
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25 changes: 21 additions & 4 deletions llvm/test/Analysis/ScalarEvolution/sext-add-inreg.ll
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@@ -1,19 +1,36 @@
; NOTE: Assertions have been autogenerated by utils/update_analyze_test_checks.py UTC_ARGS: --version 2
; RUN: opt < %s -disable-output "-passes=print<scalar-evolution>" 2>&1 | FileCheck %s

define i64 @test(i64 %a) {
; CHECK-LABEL: 'test'
; CHECK-NEXT: Classifying expressions for: @test
define i64 @test64(i64 %a) {
; CHECK-LABEL: 'test64'
; CHECK-NEXT: Classifying expressions for: @test64
; CHECK-NEXT: %add = shl i64 %a, 8
; CHECK-NEXT: --> (256 * %a) U: [0,-255) S: [-9223372036854775808,9223372036854775553)
; CHECK-NEXT: %shl = add i64 %add, 256
; CHECK-NEXT: --> (256 + (256 * %a)) U: [0,-255) S: [-9223372036854775808,9223372036854775553)
; CHECK-NEXT: %ashr = ashr exact i64 %shl, 8
; CHECK-NEXT: --> (sext i56 (1 + (trunc i64 %a to i56)) to i64) U: [-36028797018963968,36028797018963968) S: [-36028797018963968,36028797018963968)
; CHECK-NEXT: Determining loop execution counts for: @test
; CHECK-NEXT: Determining loop execution counts for: @test64
;
%add = shl i64 %a, 8
%shl = add i64 %add, 256
%ashr = ashr exact i64 %shl, 8
ret i64 %ashr
}

define i128 @test128(i128 %a) {
; CHECK-LABEL: 'test128'
; CHECK-NEXT: Classifying expressions for: @test128
; CHECK-NEXT: %shl = shl i128 %a, 4
; CHECK-NEXT: --> (16 * %a) U: [0,-15) S: [-170141183460469231731687303715884105728,170141183460469231731687303715884105713)
; CHECK-NEXT: %add = add i128 %shl, -55
; CHECK-NEXT: --> (-55 + (16 * %a)) U: [-55,-70) S: [170141183460469231731687303715884105673,170141183460469231731687303715884105658)
; CHECK-NEXT: %ashr = ashr i128 %add, 4
; CHECK-NEXT: --> (sext i124 (-4 + (trunc i128 %a to i124)) to i128) U: [-10633823966279326983230456482242756608,10633823966279326983230456482242756608) S: [-10633823966279326983230456482242756608,10633823966279326983230456482242756608)
; CHECK-NEXT: Determining loop execution counts for: @test128
;
%shl = shl i128 %a, 4
%add = add i128 %shl, -55
%ashr = ashr i128 %add, 4
ret i128 %ashr
}