[llvm] 5bfe06a - [SimplifyCFG] Use make_early_inc_range() while deleting instructions

[Heejin Ahn via llvm-commits]

Author: Heejin Ahn
Date: 2021-05-26T11:43:11-07:00
New Revision: 5bfe06ad3590d5aeb14c2fc3fae729abc6412cb3

URL: https://github.com/llvm/llvm-project/commit/5bfe06ad3590d5aeb14c2fc3fae729abc6412cb3
DIFF: https://github.com/llvm/llvm-project/commit/5bfe06ad3590d5aeb14c2fc3fae729abc6412cb3.diff

LOG: [SimplifyCFG] Use make_early_inc_range() while deleting instructions

We are deleting `phi` nodes within the for loop, so this makes sure we
increment the iterator before we delete the instruction pointed by the
iterator.

This started to break in
https://github.com/llvm/llvm-project/commit/a0be08164622bf938855ff5d19dd8e9d0c96b9b3.

Reviewed By: dschuff, lebedev.ri

Differential Revision: https://reviews.llvm.org/D103181

Added: 
    llvm/test/Transforms/SimplifyCFG/cleanup-phis.ll

Modified: 
    llvm/lib/Transforms/Utils/SimplifyCFG.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index a4a7555c9b27a..c4c828cef4029 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -4500,9 +4500,7 @@ static bool removeEmptyCleanup(CleanupReturnInst *RI, DomTreeUpdater *DTU) {
 
     // Sink any remaining PHI nodes directly into UnwindDest.
     Instruction *InsertPt = DestEHPad;
-    for (PHINode &PN : BB->phis()) {
-      // The iterator must be incremented here because the instructions are
-      // being moved to another block.
+    for (PHINode &PN : make_early_inc_range(BB->phis())) {
       if (PN.use_empty() || !PN.isUsedOutsideOfBlock(BB))
         // If the PHI node has no uses or all of its uses are in this basic
         // block (meaning they are debug or lifetime intrinsics), just leave

diff  --git a/llvm/test/Transforms/SimplifyCFG/cleanup-phis.ll b/llvm/test/Transforms/SimplifyCFG/cleanup-phis.ll
new file mode 100644
index 0000000000000..e437dc51101a8
--- /dev/null
+++ b/llvm/test/Transforms/SimplifyCFG/cleanup-phis.ll
@@ -0,0 +1,43 @@
+; RUN: opt < %s -simplifycfg -S | FileCheck %s
+
+target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
+target triple = "wasm32-unknown-unknown"
+
+; This is a regression test for a bug in which we used phis() without
+; make_early_inc_range() in a for loop while deleting phi nodes.
+
+define void @cleanup_phis() personality i8* bitcast (i32 (...)* @__gxx_wasm_personality_v0 to i8*) {
+bb0:
+  invoke void @foo()
+          to label %bb1 unwind label %ehcleanup
+
+bb1:                                              ; preds = %bb0
+  invoke void @foo()
+          to label %invoke.cont unwind label %ehcleanup
+
+invoke.cont:                                      ; preds = %bb1
+  ret void
+
+ehcleanup:                                       ; preds = %bb1, %bb0
+  %phi0 = phi i32 [ 0, %bb0 ], [ 1, %bb1 ]
+  %phi1 = phi i32 [ 2, %bb0 ], [ 3, %bb1 ]
+  %0 = cleanuppad within none []
+  cleanupret from %0 unwind label %catchswitch
+
+; These two phi nodes were originally in ehcleanup. Both phi nodes should be
+; correctly copied to this catchswitch BB.
+; CHECK: catchswitch:
+; CHECK-NEXT:  %phi0 = phi i32 [ 0, %bb0 ], [ 1, %bb1 ]
+; CHECK-NEXT:  %phi1 = phi i32 [ 2, %bb0 ], [ 3, %bb1 ]
+catchswitch:                                      ; preds = %ehcleanup
+  %1 = catchswitch within none [label %catch] unwind to caller
+
+catch:                                            ; preds = %catchswitch
+  %2 = catchpad within %1 [i8* null]
+  call void @bar(i32 %phi0, i32 %phi1)
+  unreachable
+}
+
+declare void @foo()
+declare void @bar(i32, i32)
+declare i32 @__gxx_wasm_personality_v0(...)