[TailDuplication] Add option to enable tail duplication of fallthroug…

…h BBs During TailDuplication pass, fallthrough BBs are not duplicated. This is fine for most cases, but there are cases where we want to duplicate fallthrough BBs as well (e.g. EvmEmulator). This patch adds the `tail-dup-fallthrough-bbs` option to enable tail duplication of fallthrough BBs. PR: #727. Signed-off-by: Vladimir Radosavljevic <[email protected]>
matter-labs · Oct 29, 2024 · 53efc24 · 53efc24
1 parent 4581a01
commit 53efc24
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Showing 2 changed files with 13 additions and 9 deletions.
diff --git a/llvm/lib/CodeGen/TailDuplicator.cpp b/llvm/lib/CodeGen/TailDuplicator.cpp
@@ -76,6 +76,13 @@ static cl::opt<bool>
 static cl::opt<unsigned> TailDupLimit("tail-dup-limit", cl::init(~0U),
                                       cl::Hidden);
 
+// EraVM local begin
+static cl::opt<bool>
+    TailDupFallthroughBBs("tail-dup-fallthrough-bbs",
+                          cl::desc("Tail duplicate fallthrough basic blocks"),
+                          cl::init(false), cl::Hidden);
+// EraVM local end
+
 void TailDuplicator::initMF(MachineFunction &MFin, bool PreRegAlloc,
                             const MachineBranchProbabilityInfo *MBPIin,
                             MBFIWrapper *MBFIin,
@@ -559,8 +566,10 @@ bool TailDuplicator::shouldTailDuplicate(bool IsSimple,
   // When doing tail-duplication during layout, the block ordering is in flux,
   // so canFallThrough returns a result based on incorrect information and
   // should just be ignored.
-  if (!LayoutMode && TailBB.canFallThrough())
+  // EraVM local begin
+  if (!TailDupFallthroughBBs && !LayoutMode && TailBB.canFallThrough())
     return false;
+  // EraVM local end
 
   // Don't try to tail-duplicate single-block loops.
   if (TailBB.isSuccessor(&TailBB))

diff --git a/llvm/test/CodeGen/EraVM/tail-dup-fallthrough-bbs.mir b/llvm/test/CodeGen/EraVM/tail-dup-fallthrough-bbs.mir
@@ -1,5 +1,5 @@
 # NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py UTC_ARGS: --version 2
-# RUN: llc -x mir -run-pass tailduplication -verify-machineinstrs -compile-twice=false < %s | FileCheck %s
+# RUN: llc -x mir -run-pass tailduplication -tail-dup-fallthrough-bbs -verify-machineinstrs -compile-twice=false < %s | FileCheck %s
 
 --- |
 
@@ -15,17 +15,12 @@ tracksRegLiveness: true
 body:             |
   ; CHECK-LABEL: name: test
   ; CHECK: bb.0:
-  ; CHECK-NEXT:   successors: %bb.1(0x80000000)
-  ; CHECK-NEXT:   liveins: $r1
-  ; CHECK-NEXT: {{  $}}
-  ; CHECK-NEXT:   J %bb.1
-  ; CHECK-NEXT: {{  $}}
-  ; CHECK-NEXT: bb.1:
   ; CHECK-NEXT:   successors: %bb.3(0x40000000), %bb.2(0x40000000)
   ; CHECK-NEXT:   liveins: $r1
   ; CHECK-NEXT: {{  $}}
   ; CHECK-NEXT:   dead $r0 = SUBxrr_v i256 10, $r1, i256 0, implicit-def $flags
-  ; CHECK-NEXT:   JCl %bb.3, i256 3, implicit killed $flags
+  ; CHECK-NEXT:   JCl %bb.3, 3, implicit $flags
+  ; CHECK-NEXT:   J %bb.2
   ; CHECK-NEXT: {{  $}}
   ; CHECK-NEXT: bb.2:
   ; CHECK-NEXT:   liveins: $r1