diff --git a/lib/Transforms/Scalar/SCCP.cpp b/lib/Transforms/Scalar/SCCP.cpp index 977827841d9..d8c59b1d742 100644 --- a/lib/Transforms/Scalar/SCCP.cpp +++ b/lib/Transforms/Scalar/SCCP.cpp @@ -1871,8 +1871,12 @@ bool IPSCCP::runOnModule(Module &M) { BasicBlock *DeadBB = BlocksToErase[i]; for (Value::use_iterator UI = DeadBB->use_begin(), UE = DeadBB->use_end(); UI != UE; ) { + // Grab the user and then increment the iterator early, as the user + // will be deleted. Step past all adjacent uses from the same user. + Instruction *I = dyn_cast(*UI); + do { ++UI; } while (UI != UE && *UI == I); + // Ignore blockaddress users; BasicBlock's dtor will handle them. - Instruction *I = dyn_cast(*UI++); if (!I) continue; bool Folded = ConstantFoldTerminator(I->getParent()); diff --git a/test/Transforms/IPConstantProp/user-with-multiple-uses.ll b/test/Transforms/IPConstantProp/user-with-multiple-uses.ll new file mode 100644 index 00000000000..402ea41167c --- /dev/null +++ b/test/Transforms/IPConstantProp/user-with-multiple-uses.ll @@ -0,0 +1,30 @@ +; RUN: opt < %s -S -ipsccp | FileCheck %s +; PR5596 + +; IPSCCP should propagate the 0 argument, eliminate the switch, and propagate +; the result. + +; CHECK: define i32 @main() noreturn nounwind { +; CHECK-NEXT: entry: +; CHECK-NEXT: %call2 = tail call i32 @wwrite(i64 0) nounwind +; CHECK-NEXT: ret i32 123 + +define i32 @main() noreturn nounwind { +entry: + %call2 = tail call i32 @wwrite(i64 0) nounwind + ret i32 %call2 +} + +define internal i32 @wwrite(i64 %i) nounwind readnone { +entry: + switch i64 %i, label %sw.default [ + i64 3, label %return + i64 10, label %return + ] + +sw.default: + ret i32 123 + +return: + ret i32 0 +}