From bf986a167f6270c0220befd9b5a000f7f9d635ac Mon Sep 17 00:00:00 2001
From: Andrea Shepard <andrea@persephoneslair.org>
Date: Tue, 6 Dec 2016 05:24:40 +0000
Subject: [PATCH] Implement looped version of LLVM backend h_token()
---
src/parsers/token.c | 109 +++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 108 insertions(+), 1 deletion(-)
diff --git a/src/parsers/token.c b/src/parsers/token.c
index 6f016064..3899abe8 100644
--- a/src/parsers/token.c
+++ b/src/parsers/token.c
@@ -81,7 +81,114 @@ static bool token_ctrvm(HRVMProg *prog, void *env) {
*/
static bool token_llvm_with_global(HLLVMParserCompileContext *ctxt, HToken *t) {
- /* TODO */
+ LLVMValueRef bits_args[3], bits, i, i_init, i_incr, str, str_const, len;
+ LLVMValueRef r, c, mr, icmp_i_len, icmp_c_r, rv;
+ LLVMValueRef c_gep_indices[2], c_gep;
+ LLVMBasicBlockRef entry, loop_start, loop_middle, loop_incr, success, end;
+
+ /* Set up basic blocks: entry, success and exit branches */
+ entry = LLVMAppendBasicBlock(ctxt->func, "tok_seq_entry");
+ loop_start = LLVMAppendBasicBlock(ctxt->func, "tok_seq_loop_start");
+ loop_middle = LLVMAppendBasicBlock(ctxt->func, "tok_seq_loop_middle");
+ loop_incr = LLVMAppendBasicBlock(ctxt->func, "tok_seq_loop_incr");
+ success = LLVMAppendBasicBlock(ctxt->func, "tok_seq_success");
+ end = LLVMAppendBasicBlock(ctxt->func, "tok_seq_end");
+
+ /* Branch to entry block */
+ LLVMBuildBr(ctxt->builder, entry);
+ LLVMPositionBuilderAtEnd(ctxt->builder, entry);
+
+ /*
+ * Get our string into the globals as a constant; skip the null termination
+ * and save a byte since we can compare to length in the loop.
+ */
+ str_const = LLVMConstString((const char *)(t->str), t->len, 1);
+ str = LLVMAddGlobal(ctxt->mod, LLVMArrayType(LLVMInt8Type(), t->len), "tok_str");
+ LLVMSetLinkage(str, LLVMInternalLinkage);
+ LLVMSetGlobalConstant(str, 1);
+ LLVMSetInitializer(str, str_const);
+
+ /* Have the token length available */
+ len = LLVMConstInt(ctxt->llvm_size_t, t->len, 0);
+
+ /* For each char of token... */
+ bits_args[0] = ctxt->stream;
+ bits_args[1] = LLVMConstInt(LLVMInt32Type(), 8, 0);
+ bits_args[2] = LLVMConstInt(LLVMInt8Type(), 0, 0);
+
+ /* Start the loop */
+ LLVMBuildBr(ctxt->builder, loop_start);
+ LLVMPositionBuilderAtEnd(ctxt->builder, loop_start);
+
+ /* Keep an index counter */
+ i = LLVMBuildPhi(ctxt->builder, ctxt->llvm_size_t, "i");
+ i_init = LLVMConstInt(ctxt->llvm_size_t, 0, 0);
+ /*
+ * We'll need another one once we know the value of i at the end of
+ * the loop
+ */
+ LLVMAddIncoming(i, &i_init, &entry, 1);
+
+ /*
+ * Compare i to token string length (i.e., have we hit the end of the
+ * token?); if ==, branch to success, if <, continue loop.
+ */
+ icmp_i_len = LLVMBuildICmp(ctxt->builder, LLVMIntULT, i, len, "i < len");
+ LLVMBuildCondBr(ctxt->builder, icmp_i_len, loop_middle, success);
+
+ /* Basic block loop_middle */
+ LLVMPositionBuilderAtEnd(ctxt->builder, loop_middle);
+
+ /* Get a char from the token string */
+ c_gep_indices[0] = LLVMConstInt(LLVMInt32Type(), 0, 0);
+ c_gep_indices[1] = i;
+ c_gep = LLVMBuildInBoundsGEP(ctxt->builder, str, c_gep_indices, 2, "c_p");
+ c = LLVMBuildLoad(ctxt->builder, c_gep, "c");
+
+ /* Read one char from input */
+ bits = LLVMBuildCall(ctxt->builder,
+ LLVMGetNamedFunction(ctxt->mod, "h_read_bits"), bits_args, 3, "read_bits");
+ /* Clamp to i8 */
+ r = LLVMBuildTrunc(ctxt->builder, bits, LLVMInt8Type(), "");
+
+ /*
+ * Compare c and r; if !=, token mismatches, break out of loop and
+ * fail. If ==, increment counter and go to next iteration.
+ */
+ icmp_c_r = LLVMBuildICmp(ctxt->builder, LLVMIntEQ, c, r, "c == r");
+ LLVMBuildCondBr(ctxt->builder, icmp_c_r, loop_incr, end);
+
+ /* Basic block loop_incr */
+ LLVMPositionBuilderAtEnd(ctxt->builder, loop_incr);
+ /* End of loop, 2nd LLVMAddIncoming() for i */
+ i_incr = LLVMBuildAdd(ctxt->builder, i,
+ LLVMConstInt(ctxt->llvm_size_t, 1, 0), "i_incr");
+ LLVMAddIncoming(i, &i_incr, &loop_incr, 1);
+
+ /* Next iteration */
+ LLVMBuildBr(ctxt->builder, loop_start);
+
+ /* Basic block: success */
+ LLVMPositionBuilderAtEnd(ctxt->builder, success);
+ h_llvm_make_tt_bytes_fixed(ctxt, t->str, t->len, &mr);
+ LLVMBuildBr(ctxt->builder, end);
+
+ /* Basic block: end */
+ LLVMPositionBuilderAtEnd(ctxt->builder, end);
+ /* phi the token or a null depending on where we came from */
+ rv = LLVMBuildPhi(ctxt->builder, ctxt->llvm_parseresultptr, "rv");
+ LLVMBasicBlockRef rv_phi_incoming_blocks[] = {
+ success,
+ loop_middle
+ };
+ LLVMValueRef rv_phi_incoming_values[] = {
+ mr,
+ LLVMConstNull(ctxt->llvm_parseresultptr)
+ };
+ LLVMAddIncoming(rv, rv_phi_incoming_values, rv_phi_incoming_blocks, 2);
+ /* Return it */
+ LLVMBuildRet(ctxt->builder, rv);
+
return true;
}
--
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