[PATCH] D11175: [CGP] DisableBranchOpts guards against EliminateMostlyEmptyBlocks

[Jingyue Wu]

jingyue created this revision.
jingyue added reviewers: ributzka, echristo.
jingyue added a subscriber: llvm-commits.

DisableBranchOpts is designed to disable all branch optimizations including
EliminateMostlyEmptyBlocks.

http://reviews.llvm.org/D11175

Files:
  lib/CodeGen/CodeGenPrepare.cpp
  test/Transforms/CodeGenPrepare/disable-branch-opts.ll

Index: test/Transforms/CodeGenPrepare/disable-branch-opts.ll
===================================================================
--- /dev/null
+++ test/Transforms/CodeGenPrepare/disable-branch-opts.ll
@@ -0,0 +1,20 @@
+; RUN: opt < %s -S -codegenprepare -disable-cgp-branch-opts | FileCheck %s
+
+define void @foo(i32 %x, float* %output) {
+; CHECK-LABEL: @foo(
+  %1 = icmp eq i32 %x, 1
+  br i1 %1, label %then, label %else
+
+then:
+; CHECK: then:
+  br label %merge
+
+else:
+; CHECK: else:
+  br label %merge
+
+merge:
+; CHECK: merge:
+  store float 2.0, float* %output
+  ret void
+}
Index: lib/CodeGen/CodeGenPrepare.cpp
===================================================================
--- lib/CodeGen/CodeGenPrepare.cpp
+++ lib/CodeGen/CodeGenPrepare.cpp
@@ -231,7 +231,8 @@
 
   // Eliminate blocks that contain only PHI nodes and an
   // unconditional branch.
-  EverMadeChange |= EliminateMostlyEmptyBlocks(F);
+  if (!DisableBranchOpts)
+    EverMadeChange |= EliminateMostlyEmptyBlocks(F);
 
   // llvm.dbg.value is far away from the value then iSel may not be able
   // handle it properly. iSel will drop llvm.dbg.value if it can not


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