[llvm] [InstCombine] Propagate exact flags in shift-combine transforms (PR #88340)
via llvm-commits
llvm-commits at lists.llvm.org
Sat Jun 8 20:37:42 PDT 2024
https://github.com/AtariDreams updated https://github.com/llvm/llvm-project/pull/88340
>From 64756e01167cb16fe846e71d124bc117ca86e69d Mon Sep 17 00:00:00 2001
From: Rose <gfunni234 at gmail.com>
Date: Wed, 10 Apr 2024 22:38:40 -0400
Subject: [PATCH] [InstCombine] Propagate exact flags in shift-combine
transforms
There were a couple of places where we could propagate exact flags but did not.
This patch addresses some of those places.
Alive 2 Proofs:
https://alive2.llvm.org/ce/z/vmoZrX
https://alive2.llvm.org/ce/z/9zxKKA
https://alive2.llvm.org/ce/z/HJebVu
https://alive2.llvm.org/ce/z/96ez9n
Update lshr.ll
---
.../InstCombine/InstCombineShifts.cpp | 24 ++++---
llvm/test/Transforms/InstCombine/cast.ll | 14 ++--
llvm/test/Transforms/InstCombine/lshr.ll | 28 ++++++++
llvm/test/Transforms/InstCombine/shift.ll | 70 +++++++++++++++++++
4 files changed, 121 insertions(+), 15 deletions(-)
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp b/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp
index 4a014ab6e044e..8d378f1f709f8 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp
@@ -1394,8 +1394,11 @@ Instruction *InstCombinerImpl::visitLShr(BinaryOperator &I) {
if (match(Op0,
m_OneUse(m_c_Add(m_OneUse(m_Shl(m_Value(X), m_Specific(Op1))),
m_Value(Y))))) {
- Value *NewLshr = Builder.CreateLShr(Y, Op1);
- Value *NewAdd = Builder.CreateAdd(NewLshr, X);
+ Value *NewLshr = Builder.CreateLShr(Y, Op1, "", I.isExact());
+ Value *NewAdd = Builder.CreateAdd(
+ NewLshr, X, "",
+ cast<OverflowingBinaryOperator>(Op0)->hasNoUnsignedWrap(),
+ cast<OverflowingBinaryOperator>(Op0)->hasNoSignedWrap());
unsigned Op1Val = C->getLimitedValue(BitWidth);
APInt Bits = APInt::getLowBitsSet(BitWidth, BitWidth - Op1Val);
Constant *Mask = ConstantInt::get(Ty, Bits);
@@ -1407,7 +1410,7 @@ Instruction *InstCombinerImpl::visitLShr(BinaryOperator &I) {
assert(ShAmtC < X->getType()->getScalarSizeInBits() &&
"Big shift not simplified to zero?");
// lshr (zext iM X to iN), C --> zext (lshr X, C) to iN
- Value *NewLShr = Builder.CreateLShr(X, ShAmtC);
+ Value *NewLShr = Builder.CreateLShr(X, ShAmtC, "", I.isExact());
return new ZExtInst(NewLShr, Ty);
}
@@ -1433,7 +1436,7 @@ Instruction *InstCombinerImpl::visitLShr(BinaryOperator &I) {
if (ShAmtC == BitWidth - SrcTyBitWidth) {
// The new shift amount can't be more than the narrow source type.
unsigned NewShAmt = std::min(ShAmtC, SrcTyBitWidth - 1);
- Value *AShr = Builder.CreateAShr(X, NewShAmt);
+ Value *AShr = Builder.CreateAShr(X, NewShAmt, "", I.isExact());
return new ZExtInst(AShr, Ty);
}
}
@@ -1469,9 +1472,11 @@ Instruction *InstCombinerImpl::visitLShr(BinaryOperator &I) {
// mask instruction is eliminated (and so the use check is relaxed).
if (AmtSum < SrcWidth &&
(TruncSrc->hasOneUse() || C1->uge(SrcWidth - BitWidth))) {
- Value *SumShift = Builder.CreateLShr(X, AmtSum, "sum.shift");
- Value *Trunc = Builder.CreateTrunc(SumShift, Ty, I.getName());
-
+ Value *SumShift = Builder.CreateLShr(
+ X, AmtSum, "sum.shift", TruncSrc->isExact() && I.isExact());
+ Value *Trunc = Builder.CreateTrunc(SumShift, Ty, I.getName(),
+ TruncSrc->hasNoUnsignedWrap(),
+ TruncSrc->hasNoSignedWrap());
// If the first shift does not cover the number of bits truncated, then
// we require a mask to get rid of high bits in the result.
APInt MaskC = APInt::getAllOnes(BitWidth).lshr(ShAmtC);
@@ -1709,7 +1714,10 @@ Instruction *InstCombinerImpl::visitAShr(BinaryOperator &I) {
// Oversized arithmetic shifts replicate the sign bit.
AmtSum = std::min(AmtSum, BitWidth - 1);
// (X >>s C1) >>s C2 --> X >>s (C1 + C2)
- return BinaryOperator::CreateAShr(X, ConstantInt::get(Ty, AmtSum));
+ Instruction *NewAshr =
+ BinaryOperator::CreateAShr(X, ConstantInt::get(Ty, AmtSum));
+ NewAshr->setIsExact(I.isExact() && cast<BinaryOperator>(Op0)->isExact());
+ return NewAshr;
}
if (match(Op0, m_OneUse(m_SExt(m_Value(X)))) &&
diff --git a/llvm/test/Transforms/InstCombine/cast.ll b/llvm/test/Transforms/InstCombine/cast.ll
index 6cee7bb650fd3..6abf97a7097fa 100644
--- a/llvm/test/Transforms/InstCombine/cast.ll
+++ b/llvm/test/Transforms/InstCombine/cast.ll
@@ -512,8 +512,8 @@ define <2 x i16> @test40vec_poison(<2 x i16> %a) {
; ALL-LABEL: @test40vec_poison(
; ALL-NEXT: [[T21:%.*]] = lshr <2 x i16> [[A:%.*]], <i16 9, i16 poison>
; ALL-NEXT: [[T5:%.*]] = shl <2 x i16> [[A]], <i16 8, i16 poison>
-; ALL-NEXT: [[R:%.*]] = or disjoint <2 x i16> [[T21]], [[T5]]
-; ALL-NEXT: ret <2 x i16> [[R]]
+; ALL-NEXT: [[T32:%.*]] = or disjoint <2 x i16> [[T21]], [[T5]]
+; ALL-NEXT: ret <2 x i16> [[T32]]
;
%t = zext <2 x i16> %a to <2 x i32>
%t21 = lshr <2 x i32> %t, <i32 9, i32 poison>
@@ -1993,7 +1993,7 @@ define i8 @trunc_lshr_zext(i8 %A) {
define i8 @trunc_lshr_zext_exact(i8 %A) {
; ALL-LABEL: @trunc_lshr_zext_exact(
-; ALL-NEXT: [[TMP1:%.*]] = lshr i8 [[A:%.*]], 6
+; ALL-NEXT: [[TMP1:%.*]] = lshr exact i8 [[A:%.*]], 6
; ALL-NEXT: ret i8 [[TMP1]]
;
%B = zext i8 %A to i32
@@ -2015,8 +2015,8 @@ define <2 x i8> @trunc_lshr_zext_uniform(<2 x i8> %A) {
define <2 x i8> @trunc_lshr_zext_uniform_poison(<2 x i8> %A) {
; ALL-LABEL: @trunc_lshr_zext_uniform_poison(
-; ALL-NEXT: [[D:%.*]] = lshr <2 x i8> [[A:%.*]], <i8 6, i8 poison>
-; ALL-NEXT: ret <2 x i8> [[D]]
+; ALL-NEXT: [[C:%.*]] = lshr <2 x i8> [[A:%.*]], <i8 6, i8 poison>
+; ALL-NEXT: ret <2 x i8> [[C]]
;
%B = zext <2 x i8> %A to <2 x i32>
%C = lshr <2 x i32> %B, <i32 6, i32 poison>
@@ -2037,8 +2037,8 @@ define <2 x i8> @trunc_lshr_zext_nonuniform(<2 x i8> %A) {
define <3 x i8> @trunc_lshr_zext_nonuniform_poison(<3 x i8> %A) {
; ALL-LABEL: @trunc_lshr_zext_nonuniform_poison(
-; ALL-NEXT: [[D:%.*]] = lshr <3 x i8> [[A:%.*]], <i8 6, i8 2, i8 poison>
-; ALL-NEXT: ret <3 x i8> [[D]]
+; ALL-NEXT: [[C:%.*]] = lshr <3 x i8> [[A:%.*]], <i8 6, i8 2, i8 poison>
+; ALL-NEXT: ret <3 x i8> [[C]]
;
%B = zext <3 x i8> %A to <3 x i32>
%C = lshr <3 x i32> %B, <i32 6, i32 2, i32 poison>
diff --git a/llvm/test/Transforms/InstCombine/lshr.ll b/llvm/test/Transforms/InstCombine/lshr.ll
index 60f03733ebd99..a78d493c897d1 100644
--- a/llvm/test/Transforms/InstCombine/lshr.ll
+++ b/llvm/test/Transforms/InstCombine/lshr.ll
@@ -202,6 +202,34 @@ define <2 x i8> @shl_add_commute_vec(<2 x i8> %x, <2 x i8> %py) {
ret <2 x i8> %r
}
+define i8 @shl_add2(i8 %x, i8 %y) {
+; CHECK-LABEL: @shl_add2(
+; CHECK-NEXT: [[TMP1:%.*]] = lshr exact i8 [[Y:%.*]], 2
+; CHECK-NEXT: [[TMP2:%.*]] = add i8 [[TMP1]], [[X:%.*]]
+; CHECK-NEXT: [[R:%.*]] = and i8 [[TMP2]], 63
+; CHECK-NEXT: ret i8 [[R]]
+;
+ %l = shl i8 %x, 2
+ %a = add i8 %l, %y
+ %r = lshr exact i8 %a, 2
+ ret i8 %r
+}
+
+define <2 x i8> @shl_add_commute_vec2(<2 x i8> %x, <2 x i8> %py) {
+; CHECK-LABEL: @shl_add_commute_vec2(
+; CHECK-NEXT: [[Y:%.*]] = mul <2 x i8> [[PY:%.*]], [[PY]]
+; CHECK-NEXT: [[TMP1:%.*]] = lshr exact <2 x i8> [[Y]], <i8 3, i8 3>
+; CHECK-NEXT: [[TMP2:%.*]] = add <2 x i8> [[TMP1]], [[X:%.*]]
+; CHECK-NEXT: [[R:%.*]] = and <2 x i8> [[TMP2]], <i8 31, i8 31>
+; CHECK-NEXT: ret <2 x i8> [[R]]
+;
+ %y = mul <2 x i8> %py, %py ; thwart complexity-based canonicalization
+ %l = shl <2 x i8> %x, <i8 3, i8 3>
+ %a = add <2 x i8> %y, %l
+ %r = lshr exact <2 x i8> %a, <i8 3, i8 3>
+ ret <2 x i8> %r
+}
+
define i32 @shl_add_use1(i32 %x, i32 %y) {
; CHECK-LABEL: @shl_add_use1(
; CHECK-NEXT: [[L:%.*]] = shl i32 [[X:%.*]], 2
diff --git a/llvm/test/Transforms/InstCombine/shift.ll b/llvm/test/Transforms/InstCombine/shift.ll
index 0700d7a62ee15..113c43d3c2ff9 100644
--- a/llvm/test/Transforms/InstCombine/shift.ll
+++ b/llvm/test/Transforms/InstCombine/shift.ll
@@ -433,6 +433,48 @@ entry:
ret i32 %i10
}
+define i32 @test29_exact(i64 %d18) {
+; CHECK-LABEL: @test29_exact(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[SUM_SHIFT:%.*]] = lshr exact i64 [[D18:%.*]], 63
+; CHECK-NEXT: [[I101:%.*]] = trunc nuw nsw i64 [[SUM_SHIFT]] to i32
+; CHECK-NEXT: ret i32 [[I101]]
+;
+entry:
+ %i916 = lshr exact i64 %d18, 32
+ %i917 = trunc i64 %i916 to i32
+ %i10 = lshr exact i32 %i917, 31
+ ret i32 %i10
+}
+
+define i32 @test29_exact_fail(i64 %d18) {
+; CHECK-LABEL: @test29_exact_fail(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[SUM_SHIFT:%.*]] = lshr i64 [[D18:%.*]], 63
+; CHECK-NEXT: [[I101:%.*]] = trunc nuw nsw i64 [[SUM_SHIFT]] to i32
+; CHECK-NEXT: ret i32 [[I101]]
+;
+entry:
+ %i916 = lshr exact i64 %d18, 32
+ %i917 = trunc i64 %i916 to i32
+ %i10 = lshr i32 %i917, 31
+ ret i32 %i10
+}
+
+define i32 @test29_exact_fail2(i64 %d18) {
+; CHECK-LABEL: @test29_exact_fail2(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[SUM_SHIFT:%.*]] = lshr i64 [[D18:%.*]], 63
+; CHECK-NEXT: [[I101:%.*]] = trunc nuw nsw i64 [[SUM_SHIFT]] to i32
+; CHECK-NEXT: ret i32 [[I101]]
+;
+entry:
+ %i916 = lshr i64 %d18, 32
+ %i917 = trunc i64 %i916 to i32
+ %i10 = lshr exact i32 %i917, 31
+ ret i32 %i10
+}
+
define <2 x i32> @test29_uniform(<2 x i64> %d18) {
; CHECK-LABEL: @test29_uniform(
; CHECK-NEXT: entry:
@@ -447,6 +489,34 @@ entry:
ret <2 x i32> %i10
}
+define <2 x i32> @test29_uniform_exact(<2 x i64> %d18) {
+; CHECK-LABEL: @test29_uniform_exact(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[SUM_SHIFT:%.*]] = lshr exact <2 x i64> [[D18:%.*]], <i64 63, i64 63>
+; CHECK-NEXT: [[I101:%.*]] = trunc nuw nsw <2 x i64> [[SUM_SHIFT]] to <2 x i32>
+; CHECK-NEXT: ret <2 x i32> [[I101]]
+;
+entry:
+ %i916 = lshr exact <2 x i64> %d18, <i64 32, i64 32>
+ %i917 = trunc <2 x i64> %i916 to <2 x i32>
+ %i10 = lshr exact <2 x i32> %i917, <i32 31, i32 31>
+ ret <2 x i32> %i10
+}
+
+define <2 x i32> @test29_uniform_exact_fail(<2 x i64> %d18) {
+; CHECK-LABEL: @test29_uniform_exact_fail(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[SUM_SHIFT:%.*]] = lshr <2 x i64> [[D18:%.*]], <i64 63, i64 63>
+; CHECK-NEXT: [[I101:%.*]] = trunc nuw nsw <2 x i64> [[SUM_SHIFT]] to <2 x i32>
+; CHECK-NEXT: ret <2 x i32> [[I101]]
+;
+entry:
+ %i916 = lshr <2 x i64> %d18, <i64 32, i64 32>
+ %i917 = trunc <2 x i64> %i916 to <2 x i32>
+ %i10 = lshr exact <2 x i32> %i917, <i32 31, i32 31>
+ ret <2 x i32> %i10
+}
+
define <2 x i32> @test29_nonuniform(<2 x i64> %d18) {
; CHECK-LABEL: @test29_nonuniform(
; CHECK-NEXT: entry:
More information about the llvm-commits
mailing list