[clang] [clang] Compute Switch Capacity based on number of branch-afters and fixups (PR #86815)

[via cfe-commits]

https://github.com/AtariDreams created https://github.com/llvm/llvm-project/pull/86815

None

>From 290827f07c63fa59f816b048f425d90b02a7afbe Mon Sep 17 00:00:00 2001
From: Rose <gfunni234 at gmail.com>
Date: Wed, 27 Mar 2024 11:21:18 -0400
Subject: [PATCH] [clang] Compute Switch Capacity based on number of
 branch-afters and fixups

---
 clang/lib/CodeGen/CGCleanup.cpp | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/clang/lib/CodeGen/CGCleanup.cpp b/clang/lib/CodeGen/CGCleanup.cpp
index f87caf050eeaa7..c2120d1b844c6e 100644
--- a/clang/lib/CodeGen/CGCleanup.cpp
+++ b/clang/lib/CodeGen/CGCleanup.cpp
@@ -904,19 +904,24 @@ void CodeGenFunction::PopCleanupBlock(bool FallthroughIsBranchThrough) {
                  (HasFixups && !HasEnclosingCleanups)) {
 
         llvm::BasicBlock *Default =
-          (BranchThroughDest ? BranchThroughDest : getUnreachableBlock());
-
-        // TODO: base this on the number of branch-afters and fixups
-        const unsigned SwitchCapacity = 10;
+            (BranchThroughDest ? BranchThroughDest : getUnreachableBlock());
 
         // pass the abnormal exit flag to Fn (SEH cleanup)
         cleanupFlags.setHasExitSwitch();
 
-        llvm::LoadInst *Load =
-          createLoadInstBefore(getNormalCleanupDestSlot(), "cleanup.dest",
-                               nullptr);
+        llvm::LoadInst *Load = createLoadInstBefore(getNormalCleanupDestSlot(),
+                                                    "cleanup.dest", nullptr);
+
+        unsigned numBranchAfters = Scope.getNumBranchAfters();
+        unsigned numFixups = (HasFixups && !HasEnclosingCleanups)
+                                 ? EHStack.getNumBranchFixups() - FixupDepth
+                                 : 0;
+
+        // Compute Switch Capacity based on number of branch-afters and fixups.
+        const unsigned SwitchCapacity = numBranchAfters + numFixups;
+
         llvm::SwitchInst *Switch =
-          llvm::SwitchInst::Create(Load, Default, SwitchCapacity);
+            llvm::SwitchInst::Create(Load, Default, SwitchCapacity);
 
         InstsToAppend.push_back(Load);
         InstsToAppend.push_back(Switch);