[llvm] d064182 - [SimplifyCFG] Tail-merging all blocks with `resume` terminator

[Roman Lebedev via llvm-commits]

Author: Roman Lebedev
Date: 2021-06-24T21:25:06+03:00
New Revision: d0641826121d61cbf688dc8cd4bd368939292689

URL: https://github.com/llvm/llvm-project/commit/d0641826121d61cbf688dc8cd4bd368939292689
DIFF: https://github.com/llvm/llvm-project/commit/d0641826121d61cbf688dc8cd4bd368939292689.diff

LOG: [SimplifyCFG] Tail-merging all blocks with `resume` terminator

Similar to what we already do for `ret` terminators.
As noted by @rnk, clang seems to already generate a single `ret`/`resume`,
so this isn't likely to cause widespread changes.

Reviewed By: rnk

Differential Revision: https://reviews.llvm.org/D104849

Added: 
    

Modified: 
    llvm/lib/Transforms/Scalar/SimplifyCFGPass.cpp
    llvm/test/Transforms/SimplifyCFG/tail-merge-resume.ll

Removed: 
    


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diff  --git a/llvm/lib/Transforms/Scalar/SimplifyCFGPass.cpp b/llvm/lib/Transforms/Scalar/SimplifyCFGPass.cpp
index dc21b3c726891..09d59b0e884ae 100644
--- a/llvm/lib/Transforms/Scalar/SimplifyCFGPass.cpp
+++ b/llvm/lib/Transforms/Scalar/SimplifyCFGPass.cpp
@@ -94,10 +94,15 @@ static bool tailMergeBlocksWithSimilarFunctionTerminators(Function &F,
 
     auto *Term = BB.getTerminator();
 
-    // Fow now only support `ret` function terminators.
+    // Fow now only support `ret`/`resume` function terminators.
     // FIXME: lift this restriction.
-    if (Term->getOpcode() != Instruction::Ret)
+    switch (Term->getOpcode()) {
+    case Instruction::Ret:
+    case Instruction::Resume:
+      break;
+    default:
       continue;
+    }
 
     // We can't tail-merge block that contains a musttail call.
     if (BB.getTerminatingMustTailCall())

diff  --git a/llvm/test/Transforms/SimplifyCFG/tail-merge-resume.ll b/llvm/test/Transforms/SimplifyCFG/tail-merge-resume.ll
index 2268f4371ff0e..57a0570182633 100644
--- a/llvm/test/Transforms/SimplifyCFG/tail-merge-resume.ll
+++ b/llvm/test/Transforms/SimplifyCFG/tail-merge-resume.ll
@@ -39,19 +39,20 @@ define void @merge_simple(i1 %cond) personality i8* bitcast (i32 (...)* @__gxx_p
 ; CHECK-NEXT:    cleanup
 ; CHECK-NEXT:    call void @baz()
 ; CHECK-NEXT:    br label [[RESUME2]]
+; CHECK:       common.resume:
+; CHECK-NEXT:    [[COMMON_RESUME_OP:%.*]] = phi { i8*, i32 } [ [[LP]], [[RESUME0]] ], [ [[LP]], [[RESUME1]] ], [ [[SEMICOMMON_LP:%.*]], [[RESUME2]] ]
+; CHECK-NEXT:    call void @common()
+; CHECK-NEXT:    resume { i8*, i32 } [[COMMON_RESUME_OP]]
 ; CHECK:       resume0:
 ; CHECK-NEXT:    call void @qux()
-; CHECK-NEXT:    call void @common()
-; CHECK-NEXT:    resume { i8*, i32 } [[LP]]
+; CHECK-NEXT:    br label [[COMMON_RESUME:%.*]]
 ; CHECK:       resume1:
 ; CHECK-NEXT:    call void @quux()
-; CHECK-NEXT:    call void @common()
-; CHECK-NEXT:    resume { i8*, i32 } [[LP]]
+; CHECK-NEXT:    br label [[COMMON_RESUME]]
 ; CHECK:       resume2:
-; CHECK-NEXT:    [[SEMICOMMON_LP:%.*]] = phi { i8*, i32 } [ [[LP2]], [[LPAD2]] ], [ [[LP3]], [[LPAD3]] ]
+; CHECK-NEXT:    [[SEMICOMMON_LP]] = phi { i8*, i32 } [ [[LP2]], [[LPAD2]] ], [ [[LP3]], [[LPAD3]] ]
 ; CHECK-NEXT:    call void @quuz()
-; CHECK-NEXT:    call void @common()
-; CHECK-NEXT:    resume { i8*, i32 } [[SEMICOMMON_LP]]
+; CHECK-NEXT:    br label [[COMMON_RESUME]]
 ;
   invoke void @maybe_throws() to label %invoke.cont unwind label %lpad