[PATCH] D105309: [InstCombine] Don't combine PHI before catchswitch

[Heejin Ahn via Phabricator via llvm-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rG51fecd17bbe0: [InstCombine] Don't combine PHI before catchswitch (authored by aheejin).

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D105309/new/

https://reviews.llvm.org/D105309

Files:
  llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp
  llvm/test/Transforms/InstCombine/catchswitch-phi.ll


Index: llvm/test/Transforms/InstCombine/catchswitch-phi.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/InstCombine/catchswitch-phi.ll
@@ -0,0 +1,53 @@
+; RUN: opt < %s -instcombine -S | FileCheck %s
+
+target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128-ni:1"
+target triple = "wasm32-unknown-unknown"
+
+%struct.quux = type { i32 }
+%struct.blam = type <{ %struct.quux }>
+
+declare void @foo()
+declare void @bar(%struct.quux*)
+declare i32 @__gxx_wasm_personality_v0(...)
+
+define void @test() personality i8* bitcast (i32 (...)* @__gxx_wasm_personality_v0 to i8*) {
+bb:
+  %tmp0 = alloca %struct.blam, align 4
+  br i1 undef, label %bb1, label %bb2
+
+bb1:                                              ; preds = %bb
+  %tmp1 = getelementptr inbounds %struct.blam, %struct.blam* %tmp0, i32 0, i32 0
+  invoke void @foo()
+          to label %bb3 unwind label %bb4
+
+bb2:                                              ; preds = %bb
+  %tmp2 = getelementptr inbounds %struct.blam, %struct.blam* %tmp0, i32 0, i32 0
+  invoke void @foo()
+          to label %bb3 unwind label %bb4
+
+bb3:                                              ; preds = %bb2, %bb1
+  unreachable
+
+bb4:                                              ; preds = %bb2, %bb1
+  ; This PHI should not be combined into a non-PHI instruction, because
+  ; catchswitch BB cannot have any non-PHI instruction other than catchswitch
+  ; itself.
+  ; CHECK: bb4:
+  ; CHECK-NEXT: phi
+  ; CHECK-NEXT: catchswitch
+  %tmp3 = phi %struct.quux* [ %tmp1, %bb1 ], [ %tmp2, %bb2 ]
+  %tmp4 = catchswitch within none [label %bb5] unwind label %bb7
+
+bb5:                                              ; preds = %bb4
+  %tmp5 = catchpad within %tmp4 [i8* null]
+  invoke void @foo() [ "funclet"(token %tmp5) ]
+          to label %bb6 unwind label %bb7
+
+bb6:                                              ; preds = %bb5
+  unreachable
+
+bb7:                                              ; preds = %bb5, %bb4
+  %tmp6 = cleanuppad within none []
+  call void @bar(%struct.quux* %tmp3) [ "funclet"(token %tmp6) ]
+  unreachable
+}
Index: llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp
@@ -1317,8 +1317,9 @@
       return Result;
 
   // If the incoming values are pointer casts of the same original value,
-  // replace the phi with a single cast.
-  if (PN.getType()->isPointerTy()) {
+  // replace the phi with a single cast iff we can insert a non-PHI instruction.
+  if (PN.getType()->isPointerTy() &&
+      PN.getParent()->getFirstInsertionPt() != PN.getParent()->end()) {
     Value *IV0 = PN.getIncomingValue(0);
     Value *IV0Stripped = IV0->stripPointerCasts();
     // Set to keep track of values known to be equal to IV0Stripped after


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