Mesa (lp-binning): llvmpipe: checkpoint commit of new if/else/ endif flow control
Brian Paul
brianp at kemper.freedesktop.org
Thu Jan 7 00:54:14 UTC 2010
Module: Mesa
Branch: lp-binning
Commit: baeb3a23513b9045c1a50bbe21124a4f8a9b6cd6
URL: http://cgit.freedesktop.org/mesa/mesa/commit/?id=baeb3a23513b9045c1a50bbe21124a4f8a9b6cd6
Author: Brian Paul <brianp at vmware.com>
Date: Wed Jan 6 17:53:12 2010 -0700
llvmpipe: checkpoint commit of new if/else/endif flow control
Totally untested at this point. More work to do.
---
src/gallium/drivers/llvmpipe/lp_bld_flow.c | 243 +++++++++++++++++++++++++++-
src/gallium/drivers/llvmpipe/lp_bld_flow.h | 27 +++
2 files changed, 269 insertions(+), 1 deletions(-)
diff --git a/src/gallium/drivers/llvmpipe/lp_bld_flow.c b/src/gallium/drivers/llvmpipe/lp_bld_flow.c
index e42b653..230edc6 100644
--- a/src/gallium/drivers/llvmpipe/lp_bld_flow.c
+++ b/src/gallium/drivers/llvmpipe/lp_bld_flow.c
@@ -41,6 +41,8 @@
#define LP_BUILD_FLOW_MAX_VARIABLES 32
#define LP_BUILD_FLOW_MAX_DEPTH 32
+#define LP_BUILD_IF_MAX_VARIABLES 8
+
/**
* Enumeration of all possible flow constructs.
@@ -48,6 +50,7 @@
enum lp_build_flow_construct_kind {
LP_BUILD_FLOW_SCOPE,
LP_BUILD_FLOW_SKIP,
+ LP_BUILD_FLOW_IF
};
@@ -73,7 +76,24 @@ struct lp_build_flow_skip
/** Number of variables declared at the beginning */
unsigned num_variables;
- LLVMValueRef *phi;
+ LLVMValueRef *phi; /**< array [num_variables] */
+};
+
+
+/**
+ * if/else/endif.
+ */
+struct lp_build_flow_if
+{
+ unsigned num_variables;
+
+ /** phi variables in the true clause */
+ LLVMValueRef true_variables[LP_BUILD_IF_MAX_VARIABLES];
+ unsigned num_true_variables;
+
+ /** phi variables in the false clause */
+ LLVMValueRef false_variables[LP_BUILD_IF_MAX_VARIABLES];
+ unsigned num_false_variables;
};
@@ -84,6 +104,7 @@ union lp_build_flow_construct_data
{
struct lp_build_flow_scope scope;
struct lp_build_flow_skip skip;
+ struct lp_build_flow_if ifthen;
};
@@ -540,3 +561,223 @@ lp_build_loop_end(LLVMBuilderRef builder,
LLVMPositionBuilderAtEnd(builder, after_block);
}
+
+
+/*
+ Example of if/then/else building:
+
+ int x;
+ if (cond) {
+ x = 1 + 2;
+ }
+ else {
+ x = 2 + 3;
+ }
+
+ Is built with:
+
+ flow = lp_build_flow_create(builder);
+ ...
+
+ lp_build_flow_scope_declare(flow, "x");
+
+ lp_build_if(ctx, flow, builder, cond);
+ x = LLVMAdd(1, 2);
+ lp_build_if_phi_var(ctx, "x");
+ lp_build_else(ctx);
+ x = LLVMAdd(2, 3);
+ lp_build_if_phi_var(ctx, "x");
+ lp_build_endif(ctx);
+
+ ...
+
+ flow = lp_build_flow_end(flow);
+ */
+
+
+
+/**
+ * Begin an if/else/endif construct.
+ */
+void
+lp_build_if(struct lp_build_if_state *ctx,
+ struct lp_build_flow_context *flow,
+ LLVMBuilderRef builder,
+ LLVMValueRef condition)
+{
+ LLVMBasicBlockRef block = LLVMGetInsertBlock(builder);
+ LLVMValueRef function = LLVMGetBasicBlockParent(block);
+ struct lp_build_flow_if *ifthen;
+
+ memset(ctx, 0, sizeof(*ctx));
+ ctx->builder = builder;
+ ctx->flow = flow;
+ ctx->condition = condition;
+ ctx->entry_block = block;
+
+ /* push/create new scope */
+ ifthen = &lp_build_flow_push(flow, LP_BUILD_FLOW_IF)->ifthen;
+ assert(ifthen);
+
+ ifthen->num_variables = flow->num_variables;
+ ifthen->num_true_variables = 0;
+ ifthen->num_false_variables = 0;
+
+ /* allocate the block for the if/true clause */
+ ctx->true_block = LLVMAppendBasicBlock(function, "true block");
+ /* XXX is this correct ??? */
+ LLVMPositionBuilderAtEnd(builder, ctx->true_block);
+}
+
+
+/**
+ * Begin else-part of a conditional
+ */
+void
+lp_build_else(struct lp_build_if_state *ctx)
+{
+ LLVMBasicBlockRef block = LLVMGetInsertBlock(ctx->builder);
+ LLVMValueRef function = LLVMGetBasicBlockParent(block);
+ struct lp_build_flow_if *ifthen;
+
+ ifthen = &lp_build_flow_peek(ctx->flow, LP_BUILD_FLOW_IF)->ifthen;
+ assert(ifthen);
+
+ /* allocate the block for the else/false clause */
+ ctx->false_block = LLVMAppendBasicBlock(function, "false block");
+ /* XXX is this correct ??? */
+ LLVMPositionBuilderAtEnd(ctx->builder, ctx->false_block);
+}
+
+
+/**
+ * End a conditional.
+ * This involves building a "merge" block at the endif which
+ * contains the phi instructions.
+ */
+void
+lp_build_endif(struct lp_build_if_state *ctx)
+{
+ LLVMBasicBlockRef block = LLVMGetInsertBlock(ctx->builder);
+ LLVMValueRef function = LLVMGetBasicBlockParent(block);
+ LLVMBasicBlockRef merge_block = LLVMAppendBasicBlock(function, "endif block");
+ LLVMValueRef phi[LP_BUILD_FLOW_MAX_VARIABLES];
+ struct lp_build_flow_if *ifthen;
+ unsigned i;
+
+ /* build the endif/merge block now */
+ /* XXX this is probably wrong */
+ LLVMPositionBuilderAtEnd(ctx->builder, merge_block);
+
+ ifthen = &lp_build_flow_pop(ctx->flow, LP_BUILD_FLOW_IF)->ifthen;
+ assert(ifthen);
+
+ memset(phi, 0, sizeof(phi));
+
+ /* build phi nodes for any variables which were declared inside if part */
+
+ for (i = 0; i < ifthen->num_variables; i++) {
+ LLVMValueRef *var = ctx->flow->variables[i];
+ const char *name = LLVMGetValueName(*var);
+ unsigned j;
+
+ /* search true-clause variables list for 'name' */
+ for (j = 0; j < ifthen->num_true_variables; j++) {
+ LLVMValueRef v = ifthen->true_variables[j];
+ if (strcmp(LLVMGetValueName(v), name) == 0) {
+ /* add phi */
+ if (!phi[i])
+ phi[i] = LLVMBuildPhi(ctx->builder, LLVMTypeOf(*var), "");
+ LLVMAddIncoming(phi[i], &v, &ctx->true_block, 1);
+ }
+ }
+
+ /* search false-clause variables list for 'name' */
+ for (j = 0; j < ifthen->num_false_variables; j++) {
+ LLVMValueRef v = ifthen->false_variables[j];
+ if (strcmp(LLVMGetValueName(v), name) == 0) {
+ /* add phi */
+ if (!phi[i])
+ phi[i] = LLVMBuildPhi(ctx->builder, LLVMTypeOf(*var), "");
+ LLVMAddIncoming(phi[i], &v, &ctx->false_block, 1);
+ }
+ }
+
+ /* "return" new phi variable to calling code */
+ if (phi[i])
+ *var = phi[i];
+ }
+
+ /***
+ *** Insert the various branch instructions here.
+ *** XXX need to verify all the builder/block positioning is correct.
+ ***/
+
+ /* Insert the conditional branch instruction at the end of entry_block */
+ LLVMPositionBuilderAtEnd(ctx->builder, ctx->entry_block);
+
+ if (ctx->false_block) {
+ /* we have an else clause */
+ LLVMBuildCondBr(ctx->builder, ctx->condition,
+ ctx->true_block, ctx->false_block);
+ }
+ else {
+ /* no else clause */
+ LLVMBuildCondBr(ctx->builder, ctx->condition,
+ ctx->true_block, merge_block);
+ }
+
+ /* Append an unconditional Br(anch) instruction on the true_block */
+ LLVMPositionBuilderAtEnd(ctx->builder, ctx->true_block);
+ LLVMBuildBr(ctx->builder, merge_block);
+ if (ctx->false_block) {
+ /* Append an unconditional Br(anch) instruction on the false_block */
+ LLVMPositionBuilderAtEnd(ctx->builder, ctx->false_block);
+ LLVMBuildBr(ctx->builder, merge_block);
+ }
+
+
+ /* Finish-up: continue building at end of the merge_block */
+ /* XXX is this right? */
+ LLVMPositionBuilderAtEnd(ctx->builder, merge_block);
+}
+
+
+/**
+ * Declare a variable that needs to be merged with another variable
+ * via a phi function.
+ * This function must be called after lp_build_if() and lp_build_endif().
+ */
+void
+lp_build_if_phi_var(struct lp_build_if_state *ctx, LLVMValueRef var)
+{
+ struct lp_build_flow_if *ifthen;
+ const char *name;
+
+ name = LLVMGetValueName(var);
+ assert(name && "variable requires a name");
+
+ /* make sure the var existed before the if/then/else */
+ {
+ boolean found = FALSE;
+ uint i;
+ for (i = 0; i < ctx->flow->num_variables; i++) {
+ LLVMValueRef *var = ctx->flow->variables[i];
+ if (strcmp(LLVMGetValueName(*var), name) == 0) {
+ found = TRUE;
+ break;
+ }
+ }
+ assert(found);
+ }
+
+ ifthen = &lp_build_flow_pop(ctx->flow, LP_BUILD_FLOW_IF)->ifthen;
+
+ if (ctx->false_block) {
+ ifthen->false_variables[ifthen->num_false_variables++] = var;
+ }
+ else {
+ assert(ctx->true_block);
+ ifthen->true_variables[ifthen->num_true_variables++] = var;
+ }
+}
diff --git a/src/gallium/drivers/llvmpipe/lp_bld_flow.h b/src/gallium/drivers/llvmpipe/lp_bld_flow.h
index e61999f..1f294b8 100644
--- a/src/gallium/drivers/llvmpipe/lp_bld_flow.h
+++ b/src/gallium/drivers/llvmpipe/lp_bld_flow.h
@@ -126,4 +126,31 @@ lp_build_loop_end(LLVMBuilderRef builder,
+
+struct lp_build_if_state
+{
+ LLVMBuilderRef builder;
+ struct lp_build_flow_context *flow;
+ LLVMValueRef condition;
+ LLVMBasicBlockRef entry_block, true_block, false_block;
+};
+
+
+void
+lp_build_if(struct lp_build_if_state *ctx,
+ struct lp_build_flow_context *flow,
+ LLVMBuilderRef builder,
+ LLVMValueRef condition);
+
+void
+lp_build_if_phi_var(struct lp_build_if_state *ctx, LLVMValueRef var);
+
+void
+lp_build_else(struct lp_build_if_state *ctx);
+
+void
+lp_build_endif(struct lp_build_if_state *ctx);
+
+
+
#endif /* !LP_BLD_FLOW_H */
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