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[SCCP] Can't go from overdefined to constant 

The fix for PR23999 made us mark loads of null as producing the constant
undef which upsets the lattice.  Instead, keep the load as "undefined".
This fixes PR26044.

llvm-svn: 257087
This commit is contained in:
David Majnemer 2016-01-07 19:25:39 +00:00
parent 45029d1677
commit bae945735a
2 changed files with 34 additions and 3 deletions
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6
llvm/lib/Transforms/Scalar/SCCP.cpp
View File

@ -1047,7 +1047,7 @@ void SCCPSolver::visitStoreInst(StoreInst &SI) {
// global, we can replace the load with the loaded constant value!
void SCCPSolver::visitLoadInst(LoadInst &I) {
// If this load is of a struct, just mark the result overdefined.
if (I.getType()->isStructTy())
if (I.getType()->isStructTy() || I.getType()->isMMXTy())
return markAnythingOverdefined(&I);
LatticeVal PtrVal = getValueState(I.getOperand(0));
@ -1061,9 +1061,9 @@ void SCCPSolver::visitLoadInst(LoadInst &I) {
Constant *Ptr = PtrVal.getConstant();
// load null -> null
// load null is undefined.
if (isa<ConstantPointerNull>(Ptr) && I.getPointerAddressSpace() == 0)
return markConstant(IV, &I, UndefValue::get(I.getType()));
return;
// Transform load (constant global) into the value loaded.
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Ptr)) {

31
llvm/test/Transforms/IPConstantProp/PR26044.ll Normal file
View File

@ -0,0 +1,31 @@
; RUN: opt < %s -S -ipsccp | FileCheck %s
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
define void @fn2() {
entry:
br label %if.end
for.cond1: ; preds = %if.end, %for.end
br i1 undef, label %if.end, label %if.end
if.end: ; preds = %lbl, %for.cond1
%e.2 = phi i32* [ undef, %entry ], [ null, %for.cond1 ], [ null, %for.cond1 ]
%0 = load i32, i32* %e.2, align 4
%call = call i32 @fn1(i32 %0)
br label %for.cond1
}
define internal i32 @fn1(i32 %p1) {
entry:
%tobool = icmp ne i32 %p1, 0
%cond = select i1 %tobool, i32 %p1, i32 %p1
ret i32 %cond
}
; CHECK-LABEL: define void @fn2(
; CHECK: call i32 @fn1(i32 undef)
; CHECK-LABEL: define internal i32 @fn1(
; CHECK:%[[COND:.*]] = select i1 undef, i32 undef, i32 undef
; CHECK: ret i32 %[[COND]]