/**************************************************************************
*
* Copyright 2009 VMware, Inc.
* All Rights Reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sub license, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice (including the
* next paragraph) shall be included in all copies or substantial portions
* of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.
* IN NO EVENT SHALL VMWARE AND/OR ITS SUPPLIERS BE LIABLE FOR
* ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*
**************************************************************************/
/**
* LLVM control flow build helpers.
*
* @author Jose Fonseca <jfonseca@vmware.com>
*/
#include "util/u_debug.h"
#include "util/u_memory.h"
#include "lp_bld_init.h"
#include "lp_bld_type.h"
#include "lp_bld_flow.h"
/**
* Insert a new block, right where builder is pointing to.
*
* This is useful important not only for aesthetic reasons, but also for
* performance reasons, as frequently run blocks should be laid out next to
* each other and fall-throughs maximized.
*
* See also llvm/lib/Transforms/Scalar/BasicBlockPlacement.cpp.
*
* Note: this function has no dependencies on the flow code and could
* be used elsewhere.
*/
LLVMBasicBlockRef
lp_build_insert_new_block(struct gallivm_state *gallivm, const char *name)
{
LLVMBasicBlockRef current_block;
LLVMBasicBlockRef next_block;
LLVMBasicBlockRef new_block;
/* get current basic block */
current_block = LLVMGetInsertBlock(gallivm->builder);
/* check if there's another block after this one */
next_block = LLVMGetNextBasicBlock(current_block);
if (next_block) {
/* insert the new block before the next block */
new_block = LLVMInsertBasicBlockInContext(gallivm->context, next_block, name);
}
else {
/* append new block after current block */
LLVMValueRef function = LLVMGetBasicBlockParent(current_block);
new_block = LLVMAppendBasicBlockInContext(gallivm->context, function, name);
}
return new_block;
}
/**
* Begin a "skip" block. Inside this block we can test a condition and
* skip to the end of the block if the condition is false.
*/
void
lp_build_flow_skip_begin(struct lp_build_skip_context *skip,
struct gallivm_state *gallivm)
{
skip->gallivm = gallivm;
/* create new basic block */
skip->block = lp_build_insert_new_block(gallivm, "skip");
}
/**
* Insert code to test a condition and branch to the end of the current
* skip block if the condition is true.
*/
void
lp_build_flow_skip_cond_break(struct lp_build_skip_context *skip,
LLVMValueRef cond)
{
LLVMBasicBlockRef new_block;
new_block = lp_build_insert_new_block(skip->gallivm, "");
/* if cond is true, goto skip->block, else goto new_block */
LLVMBuildCondBr(skip->gallivm->builder, cond, skip->block, new_block);
LLVMPositionBuilderAtEnd(skip->gallivm->builder, new_block);
}
void
lp_build_flow_skip_end(struct lp_build_skip_context *skip)
{
/* goto block */
LLVMBuildBr(skip->gallivm->builder, skip->block);
LLVMPositionBuilderAtEnd(skip->gallivm->builder, skip->block);
}
/**
* Check if the mask predicate is zero. If so, jump to the end of the block.
*/
void
lp_build_mask_check(struct lp_build_mask_context *mask)
{
LLVMBuilderRef builder = mask->skip.gallivm->builder;
LLVMValueRef value;
LLVMValueRef cond;
value = lp_build_mask_value(mask);
/*
* XXX this doesn't quite generate the most efficient code possible, if
* the masks are vectors which have all bits set to the same value
* in each element.
* movmskps/pmovmskb would be more efficient to get the required value
* into ordinary reg (certainly with 8 floats).
* Not sure if llvm could figure that out on its own.
*/
/* cond = (mask == 0) */
cond = LLVMBuildICmp(builder,
LLVMIntEQ,
LLVMBuildBitCast(builder, value, mask->reg_type, ""),
LLVMConstNull(mask->reg_type),
"");
/* if cond, goto end of block */
lp_build_flow_skip_cond_break(&mask->skip, cond);
}
/**
* Begin a section of code which is predicated on a mask.
* \param mask the mask context, initialized here
* \param flow the flow context
* \param type the type of the mask
* \param value storage for the mask
*/
void
lp_build_mask_begin(struct lp_build_mask_context *mask,
struct gallivm_state *gallivm,
struct lp_type type,
LLVMValueRef value)
{
memset(mask
, 0, sizeof *mask
);
mask->reg_type = LLVMIntTypeInContext(gallivm->context, type.width * type.length);
mask->var = lp_build_alloca(gallivm,
lp_build_int_vec_type(gallivm, type),
"execution_mask");
LLVMBuildStore(gallivm->builder, value, mask->var);
lp_build_flow_skip_begin(&mask->skip, gallivm);
}
LLVMValueRef
lp_build_mask_value(struct lp_build_mask_context *mask)
{
return LLVMBuildLoad(mask->skip.gallivm->builder, mask->var, "");
}
/**
* Update boolean mask with given value (bitwise AND).
* Typically used to update the quad's pixel alive/killed mask
* after depth testing, alpha testing, TGSI_OPCODE_KILL_IF, etc.
*/
void
lp_build_mask_update(struct lp_build_mask_context *mask,
LLVMValueRef value)
{
value = LLVMBuildAnd(mask->skip.gallivm->builder,
lp_build_mask_value(mask),
value, "");
LLVMBuildStore(mask->skip.gallivm->builder, value, mask->var);
}
/**
* End section of code which is predicated on a mask.
*/
LLVMValueRef
lp_build_mask_end(struct lp_build_mask_context *mask)
{
lp_build_flow_skip_end(&mask->skip);
return lp_build_mask_value(mask);
}
void
lp_build_loop_begin(struct lp_build_loop_state *state,
struct gallivm_state *gallivm,
LLVMValueRef start)
{
LLVMBuilderRef builder = gallivm->builder;
state->block = lp_build_insert_new_block(gallivm, "loop_begin");
state->counter_var = lp_build_alloca(gallivm, LLVMTypeOf(start), "loop_counter");
state->gallivm = gallivm;
LLVMBuildStore(builder, start, state->counter_var);
LLVMBuildBr(builder, state->block);
LLVMPositionBuilderAtEnd(builder, state->block);
state->counter = LLVMBuildLoad(builder, state->counter_var, "");
}
void
lp_build_loop_end_cond(struct lp_build_loop_state *state,
LLVMValueRef end,
LLVMValueRef step,
LLVMIntPredicate llvm_cond)
{
LLVMBuilderRef builder = state->gallivm->builder;
LLVMValueRef next;
LLVMValueRef cond;
LLVMBasicBlockRef after_block;
if (!step)
step = LLVMConstInt(LLVMTypeOf(end), 1, 0);
next = LLVMBuildAdd(builder, state->counter, step, "");
LLVMBuildStore(builder, next, state->counter_var);
cond = LLVMBuildICmp(builder, llvm_cond, next, end, "");
after_block = lp_build_insert_new_block(state->gallivm, "loop_end");
LLVMBuildCondBr(builder, cond, after_block, state->block);
LLVMPositionBuilderAtEnd(builder, after_block);
state->counter = LLVMBuildLoad(builder, state->counter_var, "");
}
void
lp_build_loop_end(struct lp_build_loop_state *state,
LLVMValueRef end,
LLVMValueRef step)
{
lp_build_loop_end_cond(state, end, step, LLVMIntNE);
}
/**
* Creates a c-style for loop,
* contrasts lp_build_loop as this checks condition on entry
* e.g. for(i = start; i cmp_op end; i += step)
* \param state the for loop state, initialized here
* \param gallivm the gallivm state
* \param start starting value of iterator
* \param cmp_op comparison operator used for comparing current value with end value
* \param end value used to compare against iterator
* \param step value added to iterator at end of each loop
*/
void
lp_build_for_loop_begin(struct lp_build_for_loop_state *state,
struct gallivm_state *gallivm,
LLVMValueRef start,
LLVMIntPredicate cmp_op,
LLVMValueRef end,
LLVMValueRef step)
{
LLVMBuilderRef builder = gallivm->builder;
assert(LLVMTypeOf
(start
) == LLVMTypeOf
(end
)); assert(LLVMTypeOf
(start
) == LLVMTypeOf
(step
));
state->begin = lp_build_insert_new_block(gallivm, "loop_begin");
state->step = step;
state->counter_var = lp_build_alloca(gallivm, LLVMTypeOf(start), "loop_counter");
state->gallivm = gallivm;
state->cond = cmp_op;
state->end = end;
LLVMBuildStore(builder, start, state->counter_var);
LLVMBuildBr(builder, state->begin);
LLVMPositionBuilderAtEnd(builder, state->begin);
state->counter = LLVMBuildLoad(builder, state->counter_var, "");
state->body = lp_build_insert_new_block(gallivm, "loop_body");
LLVMPositionBuilderAtEnd(builder, state->body);
}
/**
* End the for loop.
*/
void
lp_build_for_loop_end(struct lp_build_for_loop_state *state)
{
LLVMValueRef next, cond;
LLVMBuilderRef builder = state->gallivm->builder;
next = LLVMBuildAdd(builder, state->counter, state->step, "");
LLVMBuildStore(builder, next, state->counter_var);
LLVMBuildBr(builder, state->begin);
state
->exit = lp_build_insert_new_block
(state
->gallivm
, "loop_exit");
/*
* We build the comparison for the begin block here,
* if we build it earlier the output llvm ir is not human readable
* as the code produced is not in the standard begin -> body -> end order.
*/
LLVMPositionBuilderAtEnd(builder, state->begin);
cond = LLVMBuildICmp(builder, state->cond, state->counter, state->end, "");
LLVMBuildCondBr
(builder
, cond
, state
->body
, state
->exit);
LLVMPositionBuilderAtEnd
(builder
, state
->exit);}
/*
Example of if/then/else building:
int x;
if (cond) {
x = 1 + 2;
}
else {
x = 2 + 3;
}
Is built with:
// x needs an alloca variable
x = lp_build_alloca(builder, type, "x");
lp_build_if(ctx, builder, cond);
LLVMBuildStore(LLVMBuildAdd(1, 2), x);
lp_build_else(ctx);
LLVMBuildStore(LLVMBuildAdd(2, 3). x);
lp_build_endif(ctx);
*/
/**
* Begin an if/else/endif construct.
*/
void
lp_build_if(struct lp_build_if_state *ifthen,
struct gallivm_state *gallivm,
LLVMValueRef condition)
{
LLVMBasicBlockRef block = LLVMGetInsertBlock(gallivm->builder);
memset(ifthen
, 0, sizeof *ifthen
); ifthen->gallivm = gallivm;
ifthen->condition = condition;
ifthen->entry_block = block;
/* create endif/merge basic block for the phi functions */
ifthen->merge_block = lp_build_insert_new_block(gallivm, "endif-block");
/* create/insert true_block before merge_block */
ifthen->true_block =
LLVMInsertBasicBlockInContext(gallivm->context,
ifthen->merge_block,
"if-true-block");
/* successive code goes into the true block */
LLVMPositionBuilderAtEnd(gallivm->builder, ifthen->true_block);
}
/**
* Begin else-part of a conditional
*/
void
lp_build_else(struct lp_build_if_state *ifthen)
{
LLVMBuilderRef builder = ifthen->gallivm->builder;
/* Append an unconditional Br(anch) instruction on the true_block */
LLVMBuildBr(builder, ifthen->merge_block);
/* create/insert false_block before the merge block */
ifthen->false_block =
LLVMInsertBasicBlockInContext(ifthen->gallivm->context,
ifthen->merge_block,
"if-false-block");
/* successive code goes into the else block */
LLVMPositionBuilderAtEnd(builder, ifthen->false_block);
}
/**
* End a conditional.
*/
void
lp_build_endif(struct lp_build_if_state *ifthen)
{
LLVMBuilderRef builder = ifthen->gallivm->builder;
/* Insert branch to the merge block from current block */
LLVMBuildBr(builder, ifthen->merge_block);
/*
* Now patch in the various branch instructions.
*/
/* Insert the conditional branch instruction at the end of entry_block */
LLVMPositionBuilderAtEnd(builder, ifthen->entry_block);
if (ifthen->false_block) {
/* we have an else clause */
LLVMBuildCondBr(builder, ifthen->condition,
ifthen->true_block, ifthen->false_block);
}
else {
/* no else clause */
LLVMBuildCondBr(builder, ifthen->condition,
ifthen->true_block, ifthen->merge_block);
}
/* Resume building code at end of the ifthen->merge_block */
LLVMPositionBuilderAtEnd(builder, ifthen->merge_block);
}
/**
* Allocate a scalar (or vector) variable.
*
* Although not strictly part of control flow, control flow has deep impact in
* how variables should be allocated.
*
* The mem2reg optimization pass is the recommended way to dealing with mutable
* variables, and SSA. It looks for allocas and if it can handle them, it
* promotes them, but only looks for alloca instructions in the entry block of
* the function. Being in the entry block guarantees that the alloca is only
* executed once, which makes analysis simpler.
*
* See also:
* - http://www.llvm.org/docs/tutorial/OCamlLangImpl7.html#memory
*/
LLVMValueRef
lp_build_alloca(struct gallivm_state *gallivm,
LLVMTypeRef type,
const char *name)
{
LLVMBuilderRef builder = gallivm->builder;
LLVMBasicBlockRef current_block = LLVMGetInsertBlock(builder);
LLVMValueRef function = LLVMGetBasicBlockParent(current_block);
LLVMBasicBlockRef first_block = LLVMGetEntryBasicBlock(function);
LLVMValueRef first_instr = LLVMGetFirstInstruction(first_block);
LLVMBuilderRef first_builder = LLVMCreateBuilderInContext(gallivm->context);
LLVMValueRef res;
if (first_instr) {
LLVMPositionBuilderBefore(first_builder, first_instr);
} else {
LLVMPositionBuilderAtEnd(first_builder, first_block);
}
res = LLVMBuildAlloca(first_builder, type, name);
LLVMBuildStore(builder, LLVMConstNull(type), res);
LLVMDisposeBuilder(first_builder);
return res;
}
/**
* Allocate an array of scalars/vectors.
*
* mem2reg pass is not capable of promoting structs or arrays to registers, but
* we still put it in the first block anyway as failure to put allocas in the
* first block may prevent the X86 backend from successfully align the stack as
* required.
*
* Also the scalarrepl pass is supposedly more powerful and can promote
* arrays in many cases.
*
* See also:
* - http://www.llvm.org/docs/tutorial/OCamlLangImpl7.html#memory
*/
LLVMValueRef
lp_build_array_alloca(struct gallivm_state *gallivm,
LLVMTypeRef type,
LLVMValueRef count,
const char *name)
{
LLVMBuilderRef builder = gallivm->builder;
LLVMBasicBlockRef current_block = LLVMGetInsertBlock(builder);
LLVMValueRef function = LLVMGetBasicBlockParent(current_block);
LLVMBasicBlockRef first_block = LLVMGetEntryBasicBlock(function);
LLVMValueRef first_instr = LLVMGetFirstInstruction(first_block);
LLVMBuilderRef first_builder = LLVMCreateBuilderInContext(gallivm->context);
LLVMValueRef res;
if (first_instr) {
LLVMPositionBuilderBefore(first_builder, first_instr);
} else {
LLVMPositionBuilderAtEnd(first_builder, first_block);
}
res = LLVMBuildArrayAlloca(first_builder, type, count, name);
LLVMDisposeBuilder(first_builder);
return res;
}