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llvm/cbe: fix signed @mod/@divFloor computations

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Closes #15636
This commit is contained in:
Jacob Young
2023-05-10 01:56:48 -04:00
parent 31a13ce2e3
commit 2e6a6d7564
3 changed files with 62 additions and 39 deletions
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59
src/codegen/llvm.zig
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@@ -7215,20 +7215,28 @@ pub const FuncGen = struct {
return self.buildFloatOp(.floor, inst_ty, 1, .{result});
}
if (scalar_ty.isSignedInt()) {
// const d = @divTrunc(a, b);
// const r = @rem(a, b);
// return if (r == 0) d else d - ((a < 0) ^ (b < 0));
const result_llvm_ty = try self.dg.lowerType(inst_ty);
const zero = result_llvm_ty.constNull();
const div_trunc = self.builder.buildSDiv(lhs, rhs, "");
const target = self.dg.module.getTarget();
const inst_llvm_ty = try self.dg.lowerType(inst_ty);
const scalar_bit_size_minus_one = scalar_ty.bitSize(target) - 1;
const bit_size_minus_one = if (inst_ty.zigTypeTag() == .Vector) const_vector: {
const vec_len = inst_ty.vectorLen();
const scalar_llvm_ty = try self.dg.lowerType(scalar_ty);
const shifts = try self.gpa.alloc(*llvm.Value, vec_len);
defer self.gpa.free(shifts);
@memset(shifts, scalar_llvm_ty.constInt(scalar_bit_size_minus_one, .False));
break :const_vector llvm.constVector(shifts.ptr, vec_len);
} else inst_llvm_ty.constInt(scalar_bit_size_minus_one, .False);
const div = self.builder.buildSDiv(lhs, rhs, "");
const rem = self.builder.buildSRem(lhs, rhs, "");
const rem_eq_0 = self.builder.buildICmp(.EQ, rem, zero, "");
const a_lt_0 = self.builder.buildICmp(.SLT, lhs, zero, "");
const b_lt_0 = self.builder.buildICmp(.SLT, rhs, zero, "");
const a_b_xor = self.builder.buildXor(a_lt_0, b_lt_0, "");
const a_b_xor_ext = self.builder.buildZExt(a_b_xor, div_trunc.typeOf(), "");
const d_sub_xor = self.builder.buildSub(div_trunc, a_b_xor_ext, "");
return self.builder.buildSelect(rem_eq_0, div_trunc, d_sub_xor, "");
const div_sign = self.builder.buildXor(lhs, rhs, "");
const div_sign_mask = self.builder.buildAShr(div_sign, bit_size_minus_one, "");
const zero = inst_llvm_ty.constNull();
const rem_nonzero = self.builder.buildICmp(.NE, rem, zero, "");
const correction = self.builder.buildSelect(rem_nonzero, div_sign_mask, zero, "");
return self.builder.buildNSWAdd(div, correction, "");
}
return self.builder.buildUDiv(lhs, rhs, "");
}
@@ -7280,12 +7288,27 @@ pub const FuncGen = struct {
return self.builder.buildSelect(ltz, c, a, "");
}
if (scalar_ty.isSignedInt()) {
const a = self.builder.buildSRem(lhs, rhs, "");
const b = self.builder.buildNSWAdd(a, rhs, "");
const c = self.builder.buildSRem(b, rhs, "");
const target = self.dg.module.getTarget();
const scalar_bit_size_minus_one = scalar_ty.bitSize(target) - 1;
const bit_size_minus_one = if (inst_ty.zigTypeTag() == .Vector) const_vector: {
const vec_len = inst_ty.vectorLen();
const scalar_llvm_ty = try self.dg.lowerType(scalar_ty);
const shifts = try self.gpa.alloc(*llvm.Value, vec_len);
defer self.gpa.free(shifts);
@memset(shifts, scalar_llvm_ty.constInt(scalar_bit_size_minus_one, .False));
break :const_vector llvm.constVector(shifts.ptr, vec_len);
} else inst_llvm_ty.constInt(scalar_bit_size_minus_one, .False);
const rem = self.builder.buildSRem(lhs, rhs, "");
const div_sign = self.builder.buildXor(lhs, rhs, "");
const div_sign_mask = self.builder.buildAShr(div_sign, bit_size_minus_one, "");
const rhs_masked = self.builder.buildAnd(rhs, div_sign_mask, "");
const zero = inst_llvm_ty.constNull();
const ltz = self.builder.buildICmp(.SLT, lhs, zero, "");
return self.builder.buildSelect(ltz, c, a, "");
const rem_nonzero = self.builder.buildICmp(.NE, rem, zero, "");
const correction = self.builder.buildSelect(rem_nonzero, rhs_masked, zero, "");
return self.builder.buildNSWAdd(rem, correction, "");
}
return self.builder.buildURem(lhs, rhs, "");
}