[llvm] Fold X * (2^N + 1) >> N -> X when N is half the bitwidth of X (PR #92909)
via llvm-commits
llvm-commits at lists.llvm.org
Tue May 21 05:46:25 PDT 2024
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-llvm-transforms
Author: AtariDreams (AtariDreams)
<details>
<summary>Changes</summary>
This depends on #<!-- -->92907 being merged first. Once that is done, I will update the title and description of this.
---
Full diff: https://github.com/llvm/llvm-project/pull/92909.diff
4 Files Affected:
- (modified) llvm/lib/Analysis/InstructionSimplify.cpp (+39)
- (modified) llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp (+47-20)
- (modified) llvm/test/Transforms/InstCombine/ashr-lshr.ll (+281)
- (modified) llvm/test/Transforms/InstCombine/lshr.ll (+28-8)
``````````diff
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 53a974c5294c6..15f71dcb87620 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -1479,6 +1479,29 @@ static Value *simplifyLShrInst(Value *Op0, Value *Op1, bool IsExact,
if (Q.IIQ.UseInstrInfo && match(Op0, m_NUWShl(m_Value(X), m_Specific(Op1))))
return X;
+ // Look for a "splat" mul pattern - it replicates bits across each half
+ // of a value, so a right shift is just a mask of the low bits:
+ const APInt *MulC;
+ const APInt *ShAmt;
+ if (Q.IIQ.UseInstrInfo && match(Op0, m_NUWMul(m_Value(X), m_APInt(MulC))) &&
+ match(Op1, m_APInt(ShAmt))) {
+ unsigned ShAmtC = ShAmt->getZExtValue();
+ unsigned BitWidth = ShAmt->getBitWidth();
+ if (BitWidth > 2 && (*MulC - 1).isPowerOf2() &&
+ MulC->logBase2() == ShAmtC) {
+ // FIXME: This condition should be covered by the computeKnownBits, but
+ // for some reason it is not, so keep this in for now. This has no
+ // negative effects, but KnownBits should be able to infer a number of
+ // leading bits based on 2^N + 1 not wrapping, as that means 2^N must not
+ // wrap either, which means the top N bits of X must be 0.
+ if (ShAmtC * 2 == BitWidth)
+ return X;
+ const KnownBits XKnown = computeKnownBits(X, /* Depth */ 0, Q);
+ if (XKnown.countMaxActiveBits() <= ShAmtC)
+ return X;
+ }
+ }
+
// ((X << A) | Y) >> A -> X if effective width of Y is not larger than A.
// We can return X as we do in the above case since OR alters no bits in X.
// SimplifyDemandedBits in InstCombine can do more general optimization for
@@ -1523,6 +1546,22 @@ static Value *simplifyAShrInst(Value *Op0, Value *Op1, bool IsExact,
if (Q.IIQ.UseInstrInfo && match(Op0, m_NSWShl(m_Value(X), m_Specific(Op1))))
return X;
+ const APInt *MulC;
+ const APInt *ShAmt;
+ if (Q.IIQ.UseInstrInfo && match(Op0, m_NUWMul(m_Value(X), m_APInt(MulC))) &&
+ match(Op1, m_APInt(ShAmt)) &&
+ cast<OverflowingBinaryOperator>(Op0)->hasNoSignedWrap()) {
+ unsigned ShAmtC = ShAmt->getZExtValue();
+ unsigned BitWidth = ShAmt->getBitWidth();
+ if (BitWidth > 2 && (*MulC - 1).isPowerOf2() &&
+ MulC->logBase2() == ShAmtC &&
+ ShAmtC < BitWidth - 1) /* Minus 1 for the sign bit */ {
+ KnownBits KnownX = computeKnownBits(X, /* Depth */ 0, Q);
+ if (KnownX.countMaxActiveBits() <= ShAmtC)
+ return X;
+ }
+ }
+
// Arithmetic shifting an all-sign-bit value is a no-op.
unsigned NumSignBits = ComputeNumSignBits(Op0, Q.DL, 0, Q.AC, Q.CxtI, Q.DT);
if (NumSignBits == Op0->getType()->getScalarSizeInBits())
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp b/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp
index ba297111d945f..8dd0f2f61756c 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp
@@ -1456,30 +1456,42 @@ Instruction *InstCombinerImpl::visitLShr(BinaryOperator &I) {
}
const APInt *MulC;
- if (match(Op0, m_NUWMul(m_Value(X), m_APInt(MulC)))) {
- // Look for a "splat" mul pattern - it replicates bits across each half of
- // a value, so a right shift is just a mask of the low bits:
- // lshr i[2N] (mul nuw X, (2^N)+1), N --> and iN X, (2^N)-1
- // TODO: Generalize to allow more than just half-width shifts?
- if (BitWidth > 2 && ShAmtC * 2 == BitWidth && (*MulC - 1).isPowerOf2() &&
- MulC->logBase2() == ShAmtC)
- return BinaryOperator::CreateAnd(X, ConstantInt::get(Ty, *MulC - 2));
+ if (match(Op0, m_OneUse(m_NUWMul(m_Value(X), m_APInt(MulC))))) {
+ if (BitWidth > 2 && (*MulC - 1).isPowerOf2() &&
+ MulC->logBase2() == ShAmtC) {
+
+ // lshr (mul nuw (X, 2^N + 1)), N -> add nuw (X, lshr(X, N))
+ auto *NewAdd = BinaryOperator::CreateNUWAdd(
+ X, Builder.CreateLShr(X, ConstantInt::get(Ty, ShAmtC), "",
+ I.isExact()));
+ NewAdd->setHasNoSignedWrap(
+ cast<OverflowingBinaryOperator>(Op0)->hasNoSignedWrap());
+ return NewAdd;
+ }
// The one-use check is not strictly necessary, but codegen may not be
// able to invert the transform and perf may suffer with an extra mul
// instruction.
- if (Op0->hasOneUse()) {
- APInt NewMulC = MulC->lshr(ShAmtC);
- // if c is divisible by (1 << ShAmtC):
- // lshr (mul nuw x, MulC), ShAmtC -> mul nuw nsw x, (MulC >> ShAmtC)
- if (MulC->eq(NewMulC.shl(ShAmtC))) {
- auto *NewMul =
- BinaryOperator::CreateNUWMul(X, ConstantInt::get(Ty, NewMulC));
- assert(ShAmtC != 0 &&
- "lshr X, 0 should be handled by simplifyLShrInst.");
- NewMul->setHasNoSignedWrap(true);
- return NewMul;
- }
+ APInt NewMulC = MulC->lshr(ShAmtC);
+ // if c is divisible by (1 << ShAmtC):
+ // lshr (mul nuw x, MulC), ShAmtC -> mul nuw nsw x, (MulC >> ShAmtC)
+ if (MulC->eq(NewMulC.shl(ShAmtC))) {
+ auto *NewMul =
+ BinaryOperator::CreateNUWMul(X, ConstantInt::get(Ty, NewMulC));
+ assert(ShAmtC != 0 &&
+ "lshr X, 0 should be handled by simplifyLShrInst.");
+ NewMul->setHasNoSignedWrap(true);
+ return NewMul;
+ }
+ }
+
+ // lshr (mul nsw (X, 2^N + 1)), N -> add nsw (X, lshr(X, N))
+ if (match(Op0, m_OneUse(m_NSWMul(m_Value(X), m_APInt(MulC))))) {
+ if (BitWidth > 2 && (*MulC - 1).isPowerOf2() &&
+ MulC->logBase2() == ShAmtC) {
+ return BinaryOperator::CreateNSWAdd(
+ X, Builder.CreateLShr(X, ConstantInt::get(Ty, ShAmtC), "",
+ I.isExact()));
}
}
@@ -1686,6 +1698,21 @@ Instruction *InstCombinerImpl::visitAShr(BinaryOperator &I) {
if (match(Op0, m_OneUse(m_NSWSub(m_Value(X), m_Value(Y)))))
return new SExtInst(Builder.CreateICmpSLT(X, Y), Ty);
}
+
+ const APInt *MulC;
+ if (match(Op0, m_OneUse(m_NSWMul(m_Value(X), m_APInt(MulC)))) &&
+ (BitWidth > 2 && (*MulC - 1).isPowerOf2() &&
+ MulC->logBase2() == ShAmt &&
+ (ShAmt < BitWidth - 1))) /* Minus 1 for the sign bit */ {
+
+ // ashr (mul nsw (X, 2^N + 1)), N -> add nsw (X, ashr(X, N))
+ auto *NewAdd = BinaryOperator::CreateNSWAdd(
+ X,
+ Builder.CreateAShr(X, ConstantInt::get(Ty, ShAmt), "", I.isExact()));
+ NewAdd->setHasNoUnsignedWrap(
+ cast<OverflowingBinaryOperator>(Op0)->hasNoUnsignedWrap());
+ return NewAdd;
+ }
}
const SimplifyQuery Q = SQ.getWithInstruction(&I);
diff --git a/llvm/test/Transforms/InstCombine/ashr-lshr.ll b/llvm/test/Transforms/InstCombine/ashr-lshr.ll
index ac206dc7999dd..f426755dfc9dd 100644
--- a/llvm/test/Transforms/InstCombine/ashr-lshr.ll
+++ b/llvm/test/Transforms/InstCombine/ashr-lshr.ll
@@ -604,3 +604,284 @@ define <2 x i8> @ashr_known_pos_exact_vec(<2 x i8> %x, <2 x i8> %y) {
%r = ashr exact <2 x i8> %p, %y
ret <2 x i8> %r
}
+
+define i32 @lshr_mul_times_3_div_2(i32 %0) {
+; CHECK-LABEL: @lshr_mul_times_3_div_2(
+; CHECK-NEXT: [[TMP2:%.*]] = lshr i32 [[TMP0:%.*]], 1
+; CHECK-NEXT: [[LSHR:%.*]] = add nuw nsw i32 [[TMP2]], [[TMP0]]
+; CHECK-NEXT: ret i32 [[LSHR]]
+;
+ %mul = mul nsw nuw i32 %0, 3
+ %lshr = lshr i32 %mul, 1
+ ret i32 %lshr
+}
+
+define i32 @lshr_mul_times_3_div_2_exact(i32 %x) {
+; CHECK-LABEL: @lshr_mul_times_3_div_2_exact(
+; CHECK-NEXT: [[TMP1:%.*]] = lshr exact i32 [[X:%.*]], 1
+; CHECK-NEXT: [[LSHR:%.*]] = add nsw i32 [[TMP1]], [[X]]
+; CHECK-NEXT: ret i32 [[LSHR]]
+;
+ %mul = mul nsw i32 %x, 3
+ %lshr = lshr exact i32 %mul, 1
+ ret i32 %lshr
+}
+
+; Negative test
+
+define i32 @lshr_mul_times_3_div_2_no_flags(i32 %0) {
+; CHECK-LABEL: @lshr_mul_times_3_div_2_no_flags(
+; CHECK-NEXT: [[MUL:%.*]] = mul i32 [[TMP0:%.*]], 3
+; CHECK-NEXT: [[LSHR:%.*]] = lshr i32 [[MUL]], 1
+; CHECK-NEXT: ret i32 [[LSHR]]
+;
+ %mul = mul i32 %0, 3
+ %lshr = lshr i32 %mul, 1
+ ret i32 %lshr
+}
+
+; Negative test
+
+define i32 @mul_times_3_div_2_multiuse_lshr(i32 %x) {
+; CHECK-LABEL: @mul_times_3_div_2_multiuse_lshr(
+; CHECK-NEXT: [[MUL:%.*]] = mul nuw i32 [[X:%.*]], 3
+; CHECK-NEXT: [[RES:%.*]] = lshr i32 [[MUL]], 1
+; CHECK-NEXT: call void @use(i32 [[MUL]])
+; CHECK-NEXT: ret i32 [[RES]]
+;
+ %mul = mul nuw i32 %x, 3
+ %res = lshr i32 %mul, 1
+ call void @use(i32 %mul)
+ ret i32 %res
+}
+
+define i32 @lshr_mul_times_3_div_2_exact_2(i32 %x) {
+; CHECK-LABEL: @lshr_mul_times_3_div_2_exact_2(
+; CHECK-NEXT: [[TMP1:%.*]] = lshr exact i32 [[X:%.*]], 1
+; CHECK-NEXT: [[LSHR:%.*]] = add nuw i32 [[TMP1]], [[X]]
+; CHECK-NEXT: ret i32 [[LSHR]]
+;
+ %mul = mul nuw i32 %x, 3
+ %lshr = lshr exact i32 %mul, 1
+ ret i32 %lshr
+}
+
+define i32 @lshr_mul_times_5_div_4(i32 %0) {
+; CHECK-LABEL: @lshr_mul_times_5_div_4(
+; CHECK-NEXT: [[TMP2:%.*]] = lshr i32 [[TMP0:%.*]], 2
+; CHECK-NEXT: [[LSHR:%.*]] = add nuw nsw i32 [[TMP2]], [[TMP0]]
+; CHECK-NEXT: ret i32 [[LSHR]]
+;
+ %mul = mul nsw nuw i32 %0, 5
+ %lshr = lshr i32 %mul, 2
+ ret i32 %lshr
+}
+
+define i32 @lshr_mul_times_5_div_4_exact(i32 %x) {
+; CHECK-LABEL: @lshr_mul_times_5_div_4_exact(
+; CHECK-NEXT: [[TMP1:%.*]] = lshr exact i32 [[X:%.*]], 2
+; CHECK-NEXT: [[LSHR:%.*]] = add nsw i32 [[TMP1]], [[X]]
+; CHECK-NEXT: ret i32 [[LSHR]]
+;
+ %mul = mul nsw i32 %x, 5
+ %lshr = lshr exact i32 %mul, 2
+ ret i32 %lshr
+}
+
+; Negative test
+
+define i32 @lshr_mul_times_5_div_4_no_flags(i32 %0) {
+; CHECK-LABEL: @lshr_mul_times_5_div_4_no_flags(
+; CHECK-NEXT: [[MUL:%.*]] = mul i32 [[TMP0:%.*]], 5
+; CHECK-NEXT: [[LSHR:%.*]] = lshr i32 [[MUL]], 2
+; CHECK-NEXT: ret i32 [[LSHR]]
+;
+ %mul = mul i32 %0, 5
+ %lshr = lshr i32 %mul, 2
+ ret i32 %lshr
+}
+
+; Negative test
+
+define i32 @mul_times_5_div_4_multiuse_lshr(i32 %x) {
+; CHECK-LABEL: @mul_times_5_div_4_multiuse_lshr(
+; CHECK-NEXT: [[MUL:%.*]] = mul nuw i32 [[X:%.*]], 5
+; CHECK-NEXT: [[RES:%.*]] = lshr i32 [[MUL]], 2
+; CHECK-NEXT: call void @use(i32 [[MUL]])
+; CHECK-NEXT: ret i32 [[RES]]
+;
+ %mul = mul nuw i32 %x, 5
+ %res = lshr i32 %mul, 2
+ call void @use(i32 %mul)
+ ret i32 %res
+}
+
+define i32 @lshr_mul_times_5_div_4_exact_2(i32 %x) {
+; CHECK-LABEL: @lshr_mul_times_5_div_4_exact_2(
+; CHECK-NEXT: [[TMP1:%.*]] = lshr exact i32 [[X:%.*]], 2
+; CHECK-NEXT: [[LSHR:%.*]] = add nuw i32 [[TMP1]], [[X]]
+; CHECK-NEXT: ret i32 [[LSHR]]
+;
+ %mul = mul nuw i32 %x, 5
+ %lshr = lshr exact i32 %mul, 2
+ ret i32 %lshr
+}
+
+define i32 @ashr_mul_times_3_div_2(i32 %0) {
+; CHECK-LABEL: @ashr_mul_times_3_div_2(
+; CHECK-NEXT: [[TMP2:%.*]] = ashr i32 [[TMP0:%.*]], 1
+; CHECK-NEXT: [[ASHR:%.*]] = add nuw nsw i32 [[TMP2]], [[TMP0]]
+; CHECK-NEXT: ret i32 [[ASHR]]
+;
+ %mul = mul nuw nsw i32 %0, 3
+ %ashr = ashr i32 %mul, 1
+ ret i32 %ashr
+}
+
+define i32 @ashr_mul_times_3_div_2_exact(i32 %x) {
+; CHECK-LABEL: @ashr_mul_times_3_div_2_exact(
+; CHECK-NEXT: [[TMP1:%.*]] = ashr exact i32 [[X:%.*]], 1
+; CHECK-NEXT: [[ASHR:%.*]] = add nsw i32 [[TMP1]], [[X]]
+; CHECK-NEXT: ret i32 [[ASHR]]
+;
+ %mul = mul nsw i32 %x, 3
+ %ashr = ashr exact i32 %mul, 1
+ ret i32 %ashr
+}
+
+; Negative test
+
+define i32 @ashr_mul_times_3_div_2_no_flags(i32 %0) {
+; CHECK-LABEL: @ashr_mul_times_3_div_2_no_flags(
+; CHECK-NEXT: [[MUL:%.*]] = mul i32 [[TMP0:%.*]], 3
+; CHECK-NEXT: [[ASHR:%.*]] = ashr i32 [[MUL]], 1
+; CHECK-NEXT: ret i32 [[ASHR]]
+;
+ %mul = mul i32 %0, 3
+ %ashr = ashr i32 %mul, 1
+ ret i32 %ashr
+}
+
+; Negative test
+
+define i32 @ashr_mul_times_3_div_2_no_nsw(i32 %0) {
+; CHECK-LABEL: @ashr_mul_times_3_div_2_no_nsw(
+; CHECK-NEXT: [[MUL:%.*]] = mul nuw i32 [[TMP0:%.*]], 3
+; CHECK-NEXT: [[ASHR:%.*]] = ashr i32 [[MUL]], 1
+; CHECK-NEXT: ret i32 [[ASHR]]
+;
+ %mul = mul nuw i32 %0, 3
+ %ashr = ashr i32 %mul, 1
+ ret i32 %ashr
+}
+
+; Negative test
+
+define i32 @mul_times_3_div_2_multiuse_ashr(i32 %x) {
+; CHECK-LABEL: @mul_times_3_div_2_multiuse_ashr(
+; CHECK-NEXT: [[MUL:%.*]] = mul nsw i32 [[X:%.*]], 3
+; CHECK-NEXT: [[RES:%.*]] = ashr i32 [[MUL]], 1
+; CHECK-NEXT: call void @use(i32 [[MUL]])
+; CHECK-NEXT: ret i32 [[RES]]
+;
+ %mul = mul nsw i32 %x, 3
+ %res = ashr i32 %mul, 1
+ call void @use(i32 %mul)
+ ret i32 %res
+}
+
+define i32 @ashr_mul_times_3_div_2_exact_2(i32 %x) {
+; CHECK-LABEL: @ashr_mul_times_3_div_2_exact_2(
+; CHECK-NEXT: [[TMP1:%.*]] = ashr exact i32 [[X:%.*]], 1
+; CHECK-NEXT: [[ASHR:%.*]] = add nsw i32 [[TMP1]], [[X]]
+; CHECK-NEXT: ret i32 [[ASHR]]
+;
+ %mul = mul nsw i32 %x, 3
+ %ashr = ashr exact i32 %mul, 1
+ ret i32 %ashr
+}
+
+define i32 @ashr_mul_times_5_div_4(i32 %0) {
+; CHECK-LABEL: @ashr_mul_times_5_div_4(
+; CHECK-NEXT: [[TMP2:%.*]] = ashr i32 [[TMP0:%.*]], 2
+; CHECK-NEXT: [[ASHR:%.*]] = add nuw nsw i32 [[TMP2]], [[TMP0]]
+; CHECK-NEXT: ret i32 [[ASHR]]
+;
+ %mul = mul nuw nsw i32 %0, 5
+ %ashr = ashr i32 %mul, 2
+ ret i32 %ashr
+}
+
+define i32 @ashr_mul_times_5_div_4_exact(i32 %x) {
+; CHECK-LABEL: @ashr_mul_times_5_div_4_exact(
+; CHECK-NEXT: [[TMP1:%.*]] = ashr exact i32 [[X:%.*]], 2
+; CHECK-NEXT: [[ASHR:%.*]] = add nsw i32 [[TMP1]], [[X]]
+; CHECK-NEXT: ret i32 [[ASHR]]
+;
+ %mul = mul nsw i32 %x, 5
+ %ashr = ashr exact i32 %mul, 2
+ ret i32 %ashr
+}
+
+; Negative test
+
+define i32 @ashr_mul_times_5_div_4_no_flags(i32 %0) {
+; CHECK-LABEL: @ashr_mul_times_5_div_4_no_flags(
+; CHECK-NEXT: [[MUL:%.*]] = mul i32 [[TMP0:%.*]], 5
+; CHECK-NEXT: [[ASHR:%.*]] = ashr i32 [[MUL]], 2
+; CHECK-NEXT: ret i32 [[ASHR]]
+;
+ %mul = mul i32 %0, 5
+ %ashr = ashr i32 %mul, 2
+ ret i32 %ashr
+}
+
+; Negative test
+
+define i32 @mul_times_5_div_4_multiuse_ashr(i32 %x) {
+; CHECK-LABEL: @mul_times_5_div_4_multiuse_ashr(
+; CHECK-NEXT: [[MUL:%.*]] = mul nsw i32 [[X:%.*]], 5
+; CHECK-NEXT: [[RES:%.*]] = ashr i32 [[MUL]], 2
+; CHECK-NEXT: call void @use(i32 [[MUL]])
+; CHECK-NEXT: ret i32 [[RES]]
+;
+ %mul = mul nsw i32 %x, 5
+ %res = ashr i32 %mul, 2
+ call void @use(i32 %mul)
+ ret i32 %res
+}
+
+define i32 @ashr_mul_times_5_div_4_exact_2(i32 %x) {
+; CHECK-LABEL: @ashr_mul_times_5_div_4_exact_2(
+; CHECK-NEXT: [[TMP1:%.*]] = ashr exact i32 [[X:%.*]], 2
+; CHECK-NEXT: [[ASHR:%.*]] = add nsw i32 [[TMP1]], [[X]]
+; CHECK-NEXT: ret i32 [[ASHR]]
+;
+ %mul = mul nsw i32 %x, 5
+ %ashr = ashr exact i32 %mul, 2
+ ret i32 %ashr
+}
+
+define i32 @mul_splat_fold_known_active_bits(i32 %x) {
+; CHECK-LABEL: @mul_splat_fold_known_active_bits(
+; CHECK-NEXT: [[XX:%.*]] = and i32 [[X:%.*]], 360
+; CHECK-NEXT: ret i32 [[XX]]
+;
+ %xx = and i32 %x, 360
+ %m = mul nuw i32 %xx, 65537
+ %t = ashr i32 %m, 16
+ ret i32 %t
+}
+
+define i32 @mul_splat_fold_no_known_active_bits(i32 %x) {
+; CHECK-LABEL: @mul_splat_fold_no_known_active_bits(
+; CHECK-NEXT: [[TMP1:%.*]] = ashr i32 [[X:%.*]], 16
+; CHECK-NEXT: [[T:%.*]] = add nsw i32 [[TMP1]], [[X]]
+; CHECK-NEXT: ret i32 [[T]]
+;
+ %m = mul nsw i32 %x, 65537
+ %t = ashr i32 %m, 16
+ ret i32 %t
+}
+
+declare void @use(i32)
diff --git a/llvm/test/Transforms/InstCombine/lshr.ll b/llvm/test/Transforms/InstCombine/lshr.ll
index fa92c1c4b3be4..17b08985ee90e 100644
--- a/llvm/test/Transforms/InstCombine/lshr.ll
+++ b/llvm/test/Transforms/InstCombine/lshr.ll
@@ -348,22 +348,31 @@ define <2 x i32> @narrow_lshr_constant(<2 x i8> %x, <2 x i8> %y) {
define i32 @mul_splat_fold(i32 %x) {
; CHECK-LABEL: @mul_splat_fold(
-; CHECK-NEXT: [[T:%.*]] = and i32 [[X:%.*]], 65535
-; CHECK-NEXT: ret i32 [[T]]
+; CHECK-NEXT: ret i32 [[X:%.*]]
;
%m = mul nuw i32 %x, 65537
%t = lshr i32 %m, 16
ret i32 %t
}
+define i32 @mul_splat_fold_known_zeros(i32 %x) {
+; CHECK-LABEL: @mul_splat_fold_known_zeros(
+; CHECK-NEXT: [[XX:%.*]] = and i32 [[X:%.*]], 360
+; CHECK-NEXT: ret i32 [[XX]]
+;
+ %xx = and i32 %x, 360
+ %m = mul nuw i32 %xx, 65537
+ %t = lshr i32 %m, 16
+ ret i32 %t
+}
+
; Vector type, extra use, weird types are all ok.
define <3 x i14> @mul_splat_fold_vec(<3 x i14> %x) {
; CHECK-LABEL: @mul_splat_fold_vec(
; CHECK-NEXT: [[M:%.*]] = mul nuw <3 x i14> [[X:%.*]], <i14 129, i14 129, i14 129>
; CHECK-NEXT: call void @usevec(<3 x i14> [[M]])
-; CHECK-NEXT: [[T:%.*]] = and <3 x i14> [[X]], <i14 127, i14 127, i14 127>
-; CHECK-NEXT: ret <3 x i14> [[T]]
+; CHECK-NEXT: ret <3 x i14> [[X]]
;
%m = mul nuw <3 x i14> %x, <i14 129, i14 129, i14 129>
call void @usevec(<3 x i14> %m)
@@ -628,12 +637,10 @@ define i32 @mul_splat_fold_wrong_lshr_const(i32 %x) {
ret i32 %t
}
-; Negative test
-
define i32 @mul_splat_fold_no_nuw(i32 %x) {
; CHECK-LABEL: @mul_splat_fold_no_nuw(
-; CHECK-NEXT: [[M:%.*]] = mul nsw i32 [[X:%.*]], 65537
-; CHECK-NEXT: [[T:%.*]] = lshr i32 [[M]], 16
+; CHECK-NEXT: [[TMP1:%.*]] = lshr i32 [[X:%.*]], 16
+; CHECK-NEXT: [[T:%.*]] = add nsw i32 [[TMP1]], [[X]]
; CHECK-NEXT: ret i32 [[T]]
;
%m = mul nsw i32 %x, 65537
@@ -641,6 +648,19 @@ define i32 @mul_splat_fold_no_nuw(i32 %x) {
ret i32 %t
}
+; Negative test
+
+define i32 @mul_splat_fold_no_flags(i32 %x) {
+; CHECK-LABEL: @mul_splat_fold_no_flags(
+; CHECK-NEXT: [[M:%.*]] = mul i32 [[X:%.*]], 65537
+; CHECK-NEXT: [[T:%.*]] = lshr i32 [[M]], 16
+; CHECK-NEXT: ret i32 [[T]]
+;
+ %m = mul i32 %x, 65537
+ %t = lshr i32 %m, 16
+ ret i32 %t
+}
+
; Negative test (but simplifies before we reach the mul_splat transform)- need more than 2 bits
define i2 @mul_splat_fold_too_narrow(i2 %x) {
``````````
</details>
https://github.com/llvm/llvm-project/pull/92909
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