[SimplifyCFG] Prohibit hoisting of llvm.deoptimize calls

This prohibits hoisiting identical llvm.deoptimize calls
from 'then' and 'else' blocks of a conditional branch.
This fixes a crash that happened because we didn't hoist
the return instructions together with the llvm.deoptimize calls,
so the verifier would crash.

Differential Revision: https://reviews.llvm.org/D139437

diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index a1bc89e..fecf2b1 100644 (file)
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -1471,6 +1471,12 @@ static bool isSafeToHoistInstr(Instruction *I, unsigned Flags) {
   if ((Flags & SkipImplicitControlFlow) && !isSafeToSpeculativelyExecute(I))
     return false;
 
+  // Hoisting of llvm.deoptimize is only legal together with the next return
+  // instruction, which this pass is not always able to do.
+  if (auto *CB = dyn_cast<CallBase>(I))
+    if (CB->getIntrinsicID() == Intrinsic::experimental_deoptimize)
+      return false;
+
   // It's also unsafe/illegal to hoist an instruction above its instruction
   // operands
   BasicBlock *BB = I->getParent();

diff --git a/llvm/test/Transforms/SimplifyCFG/dont-hoist-deoptimize.ll b/llvm/test/Transforms/SimplifyCFG/dont-hoist-deoptimize.ll
index 456e4cd..6bfa967 100644 (file)
--- a/llvm/test/Transforms/SimplifyCFG/dont-hoist-deoptimize.ll
+++ b/llvm/test/Transforms/SimplifyCFG/dont-hoist-deoptimize.ll
@@ -1,13 +1,26 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
 ; RUN: opt -S --passes='simplifycfg<hoist-common-insts>' -simplifycfg-hoist-common-skip-limit=0 %s | FileCheck %s
 target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128-ni:1-p2:32:8:8:32-ni:2"
 target triple = "x86_64-unknown-linux-gnu"
 
 declare void @llvm.experimental.deoptimize.isVoid(...) #0
 
-; REQUIRES: asserts
-; XFAIL: *
-
 define void @widget(i1 %arg) {
+; CHECK-LABEL: @widget(
+; CHECK-NEXT:  bb:
+; CHECK-NEXT:    [[TMP:%.*]] = trunc i64 5 to i32
+; CHECK-NEXT:    br i1 [[ARG:%.*]], label [[BB1:%.*]], label [[BB4:%.*]]
+; CHECK:       bb1:
+; CHECK-NEXT:    [[TMP2:%.*]] = trunc i64 0 to i32
+; CHECK-NEXT:    [[TMP3:%.*]] = trunc i64 0 to i32
+; CHECK-NEXT:    call void (...) @llvm.experimental.deoptimize.isVoid(i32 13) #[[ATTR0:[0-9]+]] [ "deopt"() ]
+; CHECK-NEXT:    ret void
+; CHECK:       bb4:
+; CHECK-NEXT:    [[TMP6:%.*]] = trunc i64 1 to i32
+; CHECK-NEXT:    [[TMP7:%.*]] = trunc i64 0 to i32
+; CHECK-NEXT:    call void (...) @llvm.experimental.deoptimize.isVoid(i32 13) #[[ATTR0]] [ "deopt"() ]
+; CHECK-NEXT:    ret void
+;
 bb:
   br i1 %arg, label %bb1, label %bb4