[llvm] c74026d - [HotColdSplit] Mark entire function cold when entry block is cold

[Vedant Kumar via llvm-commits]

Author: Vedant Kumar
Date: 2020-02-17T15:57:50-08:00
New Revision: c74026daf36a2b8a21ccae8736772269c6467a6f

URL: https://github.com/llvm/llvm-project/commit/c74026daf36a2b8a21ccae8736772269c6467a6f
DIFF: https://github.com/llvm/llvm-project/commit/c74026daf36a2b8a21ccae8736772269c6467a6f.diff

LOG: [HotColdSplit] Mark entire function cold when entry block is cold

rdar://58855712

Added: 
    

Modified: 
    llvm/lib/Transforms/IPO/HotColdSplitting.cpp
    llvm/test/Transforms/HotColdSplit/X86/do-not-split.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/IPO/HotColdSplitting.cpp b/llvm/lib/Transforms/IPO/HotColdSplitting.cpp
index 5e690714bfdf..5fa89e2bfce3 100644
--- a/llvm/lib/Transforms/IPO/HotColdSplitting.cpp
+++ b/llvm/lib/Transforms/IPO/HotColdSplitting.cpp
@@ -458,6 +458,10 @@ class OutliningRegion {
     // first have predecessors within the extraction region.
     if (mayExtractBlock(SinkBB)) {
       addBlockToRegion(&SinkBB, SinkScore);
+      if (pred_empty(&SinkBB)) {
+        ColdRegion->EntireFunctionCold = true;
+        return Regions;
+      }
     } else {
       Regions.emplace_back();
       ColdRegion = &Regions.back();

diff  --git a/llvm/test/Transforms/HotColdSplit/X86/do-not-split.ll b/llvm/test/Transforms/HotColdSplit/X86/do-not-split.ll
index 076174d0a05e..21cd099ac703 100644
--- a/llvm/test/Transforms/HotColdSplit/X86/do-not-split.ll
+++ b/llvm/test/Transforms/HotColdSplit/X86/do-not-split.ll
@@ -50,6 +50,16 @@ if.end:                                           ; preds = %entry
   ret void
 }
 
+; Make sure we don't try to outline the entire function, especially when the
+; entry block is cold.
+; CHECK: define void @cold_entry_block() [[COLD_ATTR:#[0-9]+]]
+; CHECK-NOT: cold_entry_block.cold.1
+define void @cold_entry_block() {
+entry:
+  call void @sink()
+  ret void
+}
+
 ; Do not split `noinline` functions.
 ; CHECK-LABEL: @noinline_func
 ; CHECK-NOT: noinline_func.cold.1
@@ -182,6 +192,8 @@ if.end:                                           ; preds = %entry
   ret void
 }
 
+; CHECK: attributes [[COLD_ATTR]] = { {{.*}}cold
+
 declare void @llvm.dbg.value(metadata, metadata, metadata)
 
 declare void @sink() cold