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[InstCombine] Convert fshl(x, 0, y) to shl(x, and(y, BitWidth - 1)) when BitWidth is pow2 #122362

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Jan 11, 2025
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[InstCombine] Convert fshl(x, 0, y) to shl(x, and(y, BitWidth - 1)) when BitWidth is pow2 #122362

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[InstCombine] Add pre-commit tests
AmrDeveloper Jan 10, 2025
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[InstCombine] Convert fshl(x, 0, y) to shl(x, and(y, BitWidth - 1)) w…
AmrDeveloper Jan 11, 2025
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9 changes: 9 additions & 0 deletions llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2229,6 +2229,15 @@ Instruction *InstCombinerImpl::visitCallInst(CallInst &CI) {
return BitOp;
}

// fshl(X, 0, Y) --> shl(X, and(Y, BitWidth - 1)) if bitwidth is a
// power-of-2
if (IID == Intrinsic::fshl && isPowerOf2_32(BitWidth) &&
match(Op1, m_ZeroInt())) {
Value *Op2 = II->getArgOperand(2);
Value *And = Builder.CreateAnd(Op2, ConstantInt::get(Ty, BitWidth - 1));
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return BinaryOperator::CreateShl(Op0, And);
}

// Left or right might be masked.
if (SimplifyDemandedInstructionBits(*II))
return &CI;
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58 changes: 58 additions & 0 deletions llvm/test/Transforms/InstCombine/fsh.ll
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Expand Up @@ -1010,3 +1010,61 @@ define <2 x i32> @fshr_vec_zero_elem(<2 x i32> %x, <2 x i32> %y) {
%fsh = call <2 x i32> @llvm.fshr.v2i32(<2 x i32> %x, <2 x i32> %y, <2 x i32> <i32 2, i32 0>)
ret <2 x i32> %fsh
}

define i16 @fshl_i16_shl(i16 %x, i16 %y) {
; CHECK-LABEL: @fshl_i16_shl(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TMP0:%.*]] = and i16 [[Y:%.*]], 15
; CHECK-NEXT: [[RES:%.*]] = shl i16 [[X:%.*]], [[TMP0]]
; CHECK-NEXT: ret i16 [[RES]]
;
entry:
%res = call i16 @llvm.fshl.i16(i16 %x, i16 0, i16 %y)
ret i16 %res
}

define i32 @fshl_i32_shl(i32 %x, i32 %y) {
; CHECK-LABEL: @fshl_i32_shl(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TMP0:%.*]] = and i32 [[Y:%.*]], 31
; CHECK-NEXT: [[RES:%.*]] = shl i32 [[X:%.*]], [[TMP0]]
; CHECK-NEXT: ret i32 [[RES]]
;
entry:
%res = call i32 @llvm.fshl.i32(i32 %x, i32 0, i32 %y)
ret i32 %res
}

define <2 x i16> @fshl_vi16_shl(<2 x i16> %x, <2 x i16> %y) {
; CHECK-LABEL: @fshl_vi16_shl(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TMP0:%.*]] = and <2 x i16> [[Y:%.*]], splat (i16 15)
; CHECK-NEXT: [[RES:%.*]] = shl <2 x i16> [[X:%.*]], [[TMP0]]
; CHECK-NEXT: ret <2 x i16> [[RES]]
;
entry:
%res = call <2 x i16> @llvm.fshl.v2i16(<2 x i16> %x, <2 x i16> zeroinitializer, <2 x i16> %y)
ret <2 x i16> %res
}

define i32 @fshr_i32_shl_negative_test(i32 %x, i32 %y) {
; CHECK-LABEL: @fshr_i32_shl_negative_test(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[RES:%.*]] = call i32 @llvm.fshr.i32(i32 [[X:%.*]], i32 0, i32 [[Y:%.*]])
; CHECK-NEXT: ret i32 [[RES]]
;
entry:
%res = call i32 @llvm.fshr.i32(i32 %x, i32 0, i32 %y)
ret i32 %res
}

define <2 x i31> @fshl_vi31_shl_negative_test(<2 x i31> %x, <2 x i31> %y) {
; CHECK-LABEL: @fshl_vi31_shl_negative_test(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[RES:%.*]] = call <2 x i31> @llvm.fshl.v2i31(<2 x i31> [[X:%.*]], <2 x i31> zeroinitializer, <2 x i31> [[Y:%.*]])
; CHECK-NEXT: ret <2 x i31> [[RES]]
;
entry:
%res = call <2 x i31> @llvm.fshl.v2i31(<2 x i31> %x, <2 x i31> zeroinitializer, <2 x i31> %y)
ret <2 x i31> %res
}
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