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Compiler: Simplify codegen of arithmetic operations (#560)
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@Akuli
Akuli authored Jan 8, 2025
1 parent 0f72cbb commit 6718273
Showing 1 changed file with 56 additions and 29 deletions.
85 changes: 56 additions & 29 deletions src/codegen.c
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Original file line number Diff line number Diff line change
Expand Up @@ -240,50 +240,75 @@ static LLVMValueRef codegen_special_constant(const char *name)
return LLVMConstInt(LLVMInt1Type(), v, false);
}

static LLVMValueRef build_signed_mod(LLVMBuilderRef builder, LLVMValueRef lhs, LLVMValueRef rhs, const char *ignored)
static LLVMValueRef build_signed_mod(LLVMBuilderRef builder, LLVMValueRef lhs, LLVMValueRef rhs)
{
(void)ignored; // for compatibility with llvm functions

// Jou's % operator ensures that a%b has same sign as b:
// jou_mod(a, b) = llvm_mod(llvm_mod(a, b) + b, b)
LLVMValueRef llmod = LLVMBuildSRem(builder, lhs, rhs, "smod_tmp");
LLVMValueRef sum = LLVMBuildAdd(builder, llmod, rhs, "smod_tmp");
return LLVMBuildSRem(builder, sum, rhs, "smod");
}

static LLVMValueRef build_signed_div(LLVMBuilderRef builder, LLVMValueRef lhs, LLVMValueRef rhs, const char *ignored)
static LLVMValueRef build_signed_div(LLVMBuilderRef builder, LLVMValueRef lhs, LLVMValueRef rhs)
{
(void)ignored; // for compatibility with llvm functions
/*
LLVM's provides two divisions. One truncates, the other is an "exact div"
that requires there is no remainder. Jou uses floor division which is
neither of the two, but is quite easy to implement:
floordiv(a, b) = exact_div(a - jou_mod(a, b), b)
*/
LLVMValueRef top = LLVMBuildSub(builder, lhs, build_signed_mod(builder, lhs, rhs, NULL), "sdiv_tmp");
LLVMValueRef top = LLVMBuildSub(builder, lhs, build_signed_mod(builder, lhs, rhs), "sdiv_tmp");
return LLVMBuildExactSDiv(builder, top, rhs, "sdiv");
}

static LLVMValueRef build_num_operation(
LLVMBuilderRef builder,
LLVMValueRef lhs,
LLVMValueRef rhs,
/*
Many number operations are not the same for signed and unsigned integers.
Signed division example with 8 bits: 255 / 2 = (-1) / 2 = 0
Unsigned division example with 8 bits: 255 / 2 = 127
*/
const Type *t,
LLVMValueRef (*signedfn)(LLVMBuilderRef,LLVMValueRef,LLVMValueRef,const char*),
LLVMValueRef (*unsignedfn)(LLVMBuilderRef,LLVMValueRef,LLVMValueRef,const char*),
LLVMValueRef (*floatfn)(LLVMBuilderRef,LLVMValueRef,LLVMValueRef,const char*))
static void codegen_arithmetic_instruction(const struct State *st, const CfInstruction *ins)
{
switch(t->kind) {
case TYPE_FLOATING_POINT: return floatfn(builder, lhs, rhs, "float_op");
case TYPE_SIGNED_INTEGER: return signedfn(builder, lhs, rhs, "signed_op");
case TYPE_UNSIGNED_INTEGER: return unsignedfn(builder, lhs, rhs, "unsigned_op");
default: assert(0);
LLVMValueRef lhs = get_local_var(st, ins->operands[0]);
LLVMValueRef rhs = get_local_var(st, ins->operands[1]);

assert(ins->operands[0]->type == ins->operands[1]->type);
const Type *type = ins->operands[0]->type;

switch (type->kind) {
case TYPE_FLOATING_POINT: {
switch (ins->kind) {
case CF_NUM_ADD: set_local_var(st, ins->destvar, LLVMBuildFAdd(st->builder, lhs, rhs, "float_sum")); break;
case CF_NUM_SUB: set_local_var(st, ins->destvar, LLVMBuildFSub(st->builder, lhs, rhs, "float_diff")); break;
case CF_NUM_MUL: set_local_var(st, ins->destvar, LLVMBuildFMul(st->builder, lhs, rhs, "float_prod")); break;
case CF_NUM_DIV: set_local_var(st, ins->destvar, LLVMBuildFDiv(st->builder, lhs, rhs, "float_quot")); break;
case CF_NUM_MOD: set_local_var(st, ins->destvar, LLVMBuildFRem(st->builder, lhs, rhs, "float_mod")); break;
default: assert(0);
}
break;
}

case TYPE_SIGNED_INTEGER: {
switch (ins->kind) {
case CF_NUM_ADD: set_local_var(st, ins->destvar, LLVMBuildAdd(st->builder, lhs, rhs, "int_sum")); break;
case CF_NUM_SUB: set_local_var(st, ins->destvar, LLVMBuildSub(st->builder, lhs, rhs, "int_diff")); break;
case CF_NUM_MUL: set_local_var(st, ins->destvar, LLVMBuildMul(st->builder, lhs, rhs, "int_prod")); break;
case CF_NUM_DIV: set_local_var(st, ins->destvar, build_signed_div(st->builder, lhs, rhs)); break;
case CF_NUM_MOD: set_local_var(st, ins->destvar, build_signed_mod(st->builder, lhs, rhs)); break;
default: assert(0);
}
break;
}

case TYPE_UNSIGNED_INTEGER: {
switch (ins->kind) {
case CF_NUM_ADD: set_local_var(st, ins->destvar, LLVMBuildAdd(st->builder, lhs, rhs, "uint_sum")); break;
case CF_NUM_SUB: set_local_var(st, ins->destvar, LLVMBuildSub(st->builder, lhs, rhs, "uint_diff")); break;
case CF_NUM_MUL: set_local_var(st, ins->destvar, LLVMBuildMul(st->builder, lhs, rhs, "uint_prod")); break;
case CF_NUM_DIV: set_local_var(st, ins->destvar, LLVMBuildUDiv(st->builder, lhs, rhs, "uint_quot")); break;
case CF_NUM_MOD: set_local_var(st, ins->destvar, LLVMBuildURem(st->builder, lhs, rhs, "uint_mod")); break;
default: assert(0);
}
break;
}

default:
assert(0);
}
}

Expand Down Expand Up @@ -379,11 +404,13 @@ static void codegen_instruction(const struct State *st, const CfInstruction *ins
setdest(getop(0));
break;

case CF_NUM_ADD: setdest(build_num_operation(st->builder, getop(0), getop(1), ins->operands[0]->type, LLVMBuildAdd, LLVMBuildAdd, LLVMBuildFAdd)); break;
case CF_NUM_SUB: setdest(build_num_operation(st->builder, getop(0), getop(1), ins->operands[0]->type, LLVMBuildSub, LLVMBuildSub, LLVMBuildFSub)); break;
case CF_NUM_MUL: setdest(build_num_operation(st->builder, getop(0), getop(1), ins->operands[0]->type, LLVMBuildMul, LLVMBuildMul, LLVMBuildFMul)); break;
case CF_NUM_DIV: setdest(build_num_operation(st->builder, getop(0), getop(1), ins->operands[0]->type, build_signed_div, LLVMBuildUDiv, LLVMBuildFDiv)); break;
case CF_NUM_MOD: setdest(build_num_operation(st->builder, getop(0), getop(1), ins->operands[0]->type, build_signed_mod, LLVMBuildURem, LLVMBuildFRem)); break;
case CF_NUM_ADD:
case CF_NUM_SUB:
case CF_NUM_MUL:
case CF_NUM_DIV:
case CF_NUM_MOD:
codegen_arithmetic_instruction(st, ins);
break;

case CF_NUM_EQ:
if (is_integer_type(ins->operands[0]->type))
Expand Down

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