Allow targets to inject passes before the virtual register rewriter.

Such passes can be used to tweak the register assignments in a
target-dependent way, for example to avoid write-after-write
dependencies.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@159209 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 5 insertions, 1 deletions

diff --git a/lib/CodeGen/Passes.cpp b/lib/CodeGen/Passes.cpp
index b166dbe743..bf244a5545 100644
--- a/lib/CodeGen/Passes.cpp
+++ b/lib/CodeGen/Passes.cpp
@@ -603,7 +603,11 @@ void TargetPassConfig::addOptimizedRegAlloc(FunctionPass *RegAllocPass) {
 
   // Add the selected register allocation pass.
   PM->add(RegAllocPass);
-  printAndVerify("After Register Allocation");
+  printAndVerify("After Register Allocation, before rewriter");
+
+  // Allow targets to change the register assignments before rewriting.
+  if (addPreRewrite())
+    printAndVerify("After pre-rewrite passes");
 
   // Finally rewrite virtual registers.
   addPass(VirtRegRewriterID);