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fix PR6414, a nondeterminism issue in IPSCCP which was because 

of a subtle interation in a loop operating in densemap order.

llvm-svn: 97288
This commit is contained in:
Chris Lattner 2010-02-27 00:07:42 +00:00
parent 013b006557
commit d887f1da73
2 changed files with 47 additions and 1 deletions
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16
llvm/lib/Transforms/Scalar/SCCP.cpp
View File

@ -1918,6 +1918,14 @@ bool IPSCCP::runOnModule(Module &M) {
// all call uses with the inferred value. This means we don't need to bother
// actually returning anything from the function. Replace all return
// instructions with return undef.
//
// Do this in two stages: first identify the functions we should process, then
// actually zap their returns. This is important because we can only do this
// the address of the function isn't taken. In cases where a return is the
// last use of a function, the order of processing functions would affect
// whether we other functions are optimizable.
SmallVector<ReturnInst*, 8> ReturnsToZap;
// TODO: Process multiple value ret instructions also.
const DenseMap<Function*, LatticeVal> &RV = Solver.getTrackedRetVals();
for (DenseMap<Function*, LatticeVal>::const_iterator I = RV.begin(),
@ -1933,7 +1941,13 @@ bool IPSCCP::runOnModule(Module &M) {
for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator()))
if (!isa<UndefValue>(RI->getOperand(0)))
RI->setOperand(0, UndefValue::get(F->getReturnType()));
ReturnsToZap.push_back(RI);
}
// Zap all returns which we've identified as zap to change.
for (unsigned i = 0, e = ReturnsToZap.size(); i != e; ++i) {
Function *F = ReturnsToZap[i]->getParent()->getParent();
ReturnsToZap[i]->setOperand(0, UndefValue::get(F->getReturnType()));
}
// If we infered constant or undef values for globals variables, we can delete

32
llvm/test/Transforms/SCCP/retvalue-undef.ll Normal file
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@ -0,0 +1,32 @@
; RUN: opt -ipsccp -S %s | FileCheck %s
; PR6414
target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128"
target triple = "x86_64-unknown-linux-gnu"
define internal i32 ()* @f() {
ret i32 ()* @g
}
define internal i32 @g() {
ret i32 8
}
; CHECK: internal i32 @g()
; CHECK-NEXT: ret i32 8
define internal void @outer_mod() {
%1 = call i32 ()* ()* @f() ; <i32 ()*> [#uses=1]
%2 = call i32 %1() ; <i32> [#uses=0]
ret void
}
define internal void @module_init() {
call void @register_outer_mod(void ()* @outer_mod)
ret void
}
declare void @register_outer_mod(void ()*)
define i32 @main() {
ret i32 0
}