[InstCombine] Teach FoldPHIArgZextsIntoPHI about EHPads

FoldPHIArgZextsIntoPHI cannot insert an instruction after the PHI if
there is an EHPad in the BB.  Doing so would result in an instruction
inserted after a terminator.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@252377 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/InstCombine/InstCombinePHI.cpp

@@ -401,6 +401,12 @@ Instruction *InstCombiner::FoldPHIArgLoadIntoPHI(PHINode &PN) {
 /// require special-casing a cast from the 'i1' type. See the comment in
 /// FoldPHIArgOpIntoPHI() about pessimizing illegal integer types.
 Instruction *InstCombiner::FoldPHIArgZextsIntoPHI(PHINode &Phi) {
+  // We cannot create a new instruction after the PHI if the terminator is an
+  // EHPad because there is no valid insertion point.
+  if (TerminatorInst *TI = Phi.getParent()->getTerminator())
+    if (TI->isEHPad())
+      return nullptr;
+
   // Early exit for the common case of a phi with two operands. These are
   // handled elsewhere. See the comment below where we check the count of zexts
   // and constants for more details.

test/Transforms/InstCombine/token.ll

@@ -48,10 +48,50 @@ endpad:
   catchendpad unwind to caller
 }
 
-
 ; CHECK-LABEL: define void @test2(
 ; CHECK:  %X = zext i8 %A to i32
 ; CHECK:  %Y = zext i8 %B to i32
 ; CHECK:  %phi = phi i32 [ %X, %bb ], [ %Y, %cont ]
 
+define void @test3(i8 %A, i8 %B) personality i32 (...)* @__CxxFrameHandler3 {
+bb:
+  %X = zext i8 %A to i32
+  invoke void @g(i32 0)
+    to label %cont
+    unwind label %catch
+
+cont:
+  %Y = zext i8 %B to i32
+  invoke void @g(i32 0)
+    to label %cont2
+    unwind label %catch
+
+cont2:
+  invoke void @g(i32 0)
+    to label %unreachable
+    unwind label %catch
+
+catch:
+  %phi = phi i32 [ %X, %bb ], [ %Y, %cont ], [ %Y, %cont2 ]
+  %cl = catchpad []
+   to label %doit
+   unwind label %endpad
+
+doit:
+  call void @g(i32 %phi)
+  unreachable
+
+unreachable:
+  unreachable
+
+endpad:
+  catchendpad unwind to caller
+}
+
+; CHECK-LABEL: define void @test3(
+; CHECK:  %X = zext i8 %A to i32
+; CHECK:  %Y = zext i8 %B to i32
+; CHECK:  %phi = phi i32 [ %X, %bb ], [ %Y, %cont ], [ %Y, %cont2 ]
+
+
 declare void @g(i32)