[llvm] r280932 - [SDAGBuilder] Don't create a binary tree for switches in minsize mode

[James Molloy via llvm-commits]

Author: jamesm
Date: Thu Sep  8 08:12:22 2016
New Revision: 280932

URL: http://llvm.org/viewvc/llvm-project?rev=280932&view=rev
Log:
[SDAGBuilder] Don't create a binary tree for switches in minsize mode

This bloats codesize - all of the non-leaf nodes are extra code.

Added:
    llvm/trunk/test/CodeGen/ARM/switch-minsize.ll
Modified:
    llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp?rev=280932&r1=280931&r2=280932&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp Thu Sep  8 08:12:22 2016
@@ -9237,7 +9237,8 @@ void SelectionDAGBuilder::visitSwitch(co
     WorkList.pop_back();
     unsigned NumClusters = W.LastCluster - W.FirstCluster + 1;
 
-    if (NumClusters > 3 && TM.getOptLevel() != CodeGenOpt::None) {
+    if (NumClusters > 3 && TM.getOptLevel() != CodeGenOpt::None &&
+        !DefaultMBB->getParent()->getFunction()->optForMinSize()) {
       // For optimized builds, lower large range as a balanced binary tree.
       splitWorkItem(WorkList, W, SI.getCondition(), SwitchMBB);
       continue;

Added: llvm/trunk/test/CodeGen/ARM/switch-minsize.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/ARM/switch-minsize.ll?rev=280932&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/ARM/switch-minsize.ll (added)
+++ llvm/trunk/test/CodeGen/ARM/switch-minsize.ll Thu Sep  8 08:12:22 2016
@@ -0,0 +1,34 @@
+; RUN: llc < %s | FileCheck %s
+
+target datalayout = "e-m:o-p:32:32-f64:32:64-v64:32:64-v128:32:128-a:0:32-n32-S32"
+target triple = "thumbv7-apple-ios8.0.0"
+
+; CHECK: beq
+; CHECK: beq
+; CHECK: beq
+; CHECK: cbnz
+declare void @g(i32)
+define void @f(i32 %val) optsize minsize {
+  switch i32 %val, label %def [
+    i32 0, label %one
+    i32 9, label %two
+    i32 994, label %three
+    i32 1154, label %four
+  ]
+  
+one:
+  call void @g(i32 1)
+  ret void
+two:
+  call void @g(i32 001)
+  ret void
+three:
+  call void @g(i32 78)
+  ret void
+four:
+  call void @g(i32 87)
+  ret void
+def:
+  call void @g(i32 11)
+  ret void
+}