Disable loop re-rotation for -Oz (patch by Andrey Turetsky)

alexey-bataev · alexey-bataev · commit da33d80e9a25 · 2015-07-10T10:37:09.000Z
After changes in rL231820 loop re-rotation is performed even in -Oz mode. Since loop rotation is disabled for -Oz, it seems loop re-rotation should be disabled too. Differential Revision: http://reviews.llvm.org/D10961 llvm-svn: 241897
diff --git a/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp b/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
@@ -320,8 +320,8 @@ void PassManagerBuilder::populateModulePassManager(
 
   // Re-rotate loops in all our loop nests. These may have fallout out of
   // rotated form due to GVN or other transformations, and the vectorizer relies
-  // on the rotated form.
-  MPM.add(createLoopRotatePass());
+  // on the rotated form. Disable header duplication at -Oz.
+  MPM.add(createLoopRotatePass(SizeLevel == 2 ? 0 : -1));
 
   // Distribute loops to allow partial vectorization.  I.e. isolate dependences
   // into separate loop that would otherwise inhibit vectorization.
diff --git a/llvm/test/Transforms/LoopRotate/oz-disable.ll b/llvm/test/Transforms/LoopRotate/oz-disable.ll
@@ -0,0 +1,30 @@
+; REQUIRES: asserts
+; RUN: opt < %s -S -Os -debug -debug-only=loop-rotate 2>&1 | FileCheck %s -check-prefix=OS
+; RUN: opt < %s -S -Oz -debug -debug-only=loop-rotate 2>&1 | FileCheck %s -check-prefix=OZ
+
+; Loop should be rotated for -Os but not for -Oz.
+; OS: rotating Loop at depth 1
+; OZ-NOT: rotating Loop at depth 1
+
+@e = global i32 10
+
+declare void @use(i32)
+
+define void @test() {
+entry:
+  %end = load i32, i32* @e
+  br label %loop
+
+loop:
+  %n.phi = phi i32 [ %n, %loop.fin ], [ 0, %entry ]
+  %cond = icmp eq i32 %n.phi, %end
+  br i1 %cond, label %exit, label %loop.fin
+
+loop.fin:
+  %n = add i32 %n.phi, 1
+  call void @use(i32 %n)
+  br label %loop
+
+exit:
+  ret void
+}
