Add a speculative execution pass
Summary:
This is a pass for speculative execution of instructions for simple if-then (triangle) control flow. It's aimed at GPUs, but could perhaps be used in other contexts. Enabling this pass gives us a 1.0% geomean improvement on Google benchmark suites, with one benchmark improving 33%.
Credit goes to Jingyue Wu for writing an earlier version of this pass.
Patched by Bjarke Roune.
Test Plan:
This patch adds a set of tests in test/Transforms/SpeculativeExecution/spec.ll
The pass is controlled by a flag which defaults to having the pass not run.
Reviewers: eliben, dberlin, meheff, jingyue, hfinkel
Reviewed By: jingyue, hfinkel
Subscribers: majnemer, jholewinski, llvm-commits
Differential Revision: http://reviews.llvm.org/D9360
llvm-svn: 237459
diff --git a/llvm/lib/IR/BasicBlock.cpp b/llvm/lib/IR/BasicBlock.cpp
index 23ec705..e6a4585 100644
--- a/llvm/lib/IR/BasicBlock.cpp
+++ b/llvm/lib/IR/BasicBlock.cpp
@@ -238,6 +238,14 @@
return PredBB;
}
+BasicBlock *BasicBlock::getSingleSuccessor() {
+ succ_iterator SI = succ_begin(this), E = succ_end(this);
+ if (SI == E) return nullptr; // no successors
+ BasicBlock *TheSucc = *SI;
+ ++SI;
+ return (SI == E) ? TheSucc : nullptr /* multiple successors */;
+}
+
BasicBlock *BasicBlock::getUniqueSuccessor() {
succ_iterator SI = succ_begin(this), E = succ_end(this);
if (SI == E) return NULL; // No successors