[llvm] r276008 - [FunctionAttrs] Correct the safety analysis for inference of 'returned'
David Majnemer via llvm-commits
llvm-commits at lists.llvm.org
Tue Jul 19 11:50:30 PDT 2016
Author: majnemer
Date: Tue Jul 19 13:50:26 2016
New Revision: 276008
URL: http://llvm.org/viewvc/llvm-project?rev=276008&view=rev
Log:
[FunctionAttrs] Correct the safety analysis for inference of 'returned'
We skipped over ReturnInsts which didn't return an argument which would
lead us to incorrectly conclude that an argument returned by another
ReturnInst was 'returned'.
This reverts commit r275756.
This fixes PR28610.
Modified:
llvm/trunk/lib/Transforms/IPO/FunctionAttrs.cpp
llvm/trunk/test/Transforms/FunctionAttrs/2009-01-02-LocalStores.ll
llvm/trunk/test/Transforms/FunctionAttrs/nocapture.ll
llvm/trunk/test/Transforms/FunctionAttrs/readattrs.ll
Modified: llvm/trunk/lib/Transforms/IPO/FunctionAttrs.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/IPO/FunctionAttrs.cpp?rev=276008&r1=276007&r2=276008&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/IPO/FunctionAttrs.cpp (original)
+++ llvm/trunk/lib/Transforms/IPO/FunctionAttrs.cpp Tue Jul 19 13:50:26 2016
@@ -42,6 +42,7 @@ using namespace llvm;
STATISTIC(NumReadNone, "Number of functions marked readnone");
STATISTIC(NumReadOnly, "Number of functions marked readonly");
STATISTIC(NumNoCapture, "Number of arguments marked nocapture");
+STATISTIC(NumReturned, "Number of arguments marked returned");
STATISTIC(NumReadNoneArg, "Number of arguments marked readnone");
STATISTIC(NumReadOnlyArg, "Number of arguments marked readonly");
STATISTIC(NumNoAlias, "Number of function returns marked noalias");
@@ -483,6 +484,54 @@ determinePointerReadAttrs(Argument *A,
return IsRead ? Attribute::ReadOnly : Attribute::ReadNone;
}
+/// Deduce returned attributes for the SCC.
+static bool addArgumentReturnedAttrs(const SCCNodeSet &SCCNodes) {
+ bool Changed = false;
+
+ AttrBuilder B;
+ B.addAttribute(Attribute::Returned);
+
+ // Check each function in turn, determining if an argument is always returned.
+ for (Function *F : SCCNodes) {
+ // We can infer and propagate function attributes only when we know that the
+ // definition we'll get at link time is *exactly* the definition we see now.
+ // For more details, see GlobalValue::mayBeDerefined.
+ if (!F->hasExactDefinition())
+ continue;
+
+ if (F->getReturnType()->isVoidTy())
+ continue;
+
+ auto FindRetArg = [&]() -> Value * {
+ Value *RetArg = nullptr;
+ for (BasicBlock &BB : *F)
+ if (auto *Ret = dyn_cast<ReturnInst>(BB.getTerminator())) {
+ // Note that stripPointerCasts should look through functions with
+ // returned arguments.
+ Value *RetVal = Ret->getReturnValue()->stripPointerCasts();
+ if (!isa<Argument>(RetVal) || RetVal->getType() != F->getReturnType())
+ return nullptr;
+
+ if (!RetArg)
+ RetArg = RetVal;
+ else if (RetArg != RetVal)
+ return nullptr;
+ }
+
+ return RetArg;
+ };
+
+ if (Value *RetArg = FindRetArg()) {
+ auto *A = cast<Argument>(RetArg);
+ A->addAttr(AttributeSet::get(F->getContext(), A->getArgNo() + 1, B));
+ ++NumReturned;
+ Changed = true;
+ }
+ }
+
+ return Changed;
+}
+
/// Deduce nocapture attributes for the SCC.
static bool addArgumentAttrs(const SCCNodeSet &SCCNodes) {
bool Changed = false;
@@ -1024,6 +1073,7 @@ PreservedAnalyses PostOrderFunctionAttrs
}
bool Changed = false;
+ Changed |= addArgumentReturnedAttrs(SCCNodes);
Changed |= addReadAttrs(SCCNodes, AARGetter);
Changed |= addArgumentAttrs(SCCNodes);
@@ -1089,6 +1139,7 @@ static bool runImpl(CallGraphSCC &SCC, A
SCCNodes.insert(F);
}
+ Changed |= addArgumentReturnedAttrs(SCCNodes);
Changed |= addReadAttrs(SCCNodes, AARGetter);
Changed |= addArgumentAttrs(SCCNodes);
Modified: llvm/trunk/test/Transforms/FunctionAttrs/2009-01-02-LocalStores.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/FunctionAttrs/2009-01-02-LocalStores.ll?rev=276008&r1=276007&r2=276008&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/FunctionAttrs/2009-01-02-LocalStores.ll (original)
+++ llvm/trunk/test/Transforms/FunctionAttrs/2009-01-02-LocalStores.ll Tue Jul 19 13:50:26 2016
@@ -14,7 +14,7 @@ define i32* @b(i32 *%q) {
ret i32* %tmp
}
-; CHECK: define i32* @c(i32* readnone %r)
+; CHECK: define i32* @c(i32* readnone returned %r)
@g = global i32 0
define i32* @c(i32 *%r) {
%a = icmp eq i32* %r, null
Modified: llvm/trunk/test/Transforms/FunctionAttrs/nocapture.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/FunctionAttrs/nocapture.ll?rev=276008&r1=276007&r2=276008&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/FunctionAttrs/nocapture.ll (original)
+++ llvm/trunk/test/Transforms/FunctionAttrs/nocapture.ll Tue Jul 19 13:50:26 2016
@@ -1,7 +1,7 @@
; RUN: opt < %s -functionattrs -S | FileCheck %s
@g = global i32* null ; <i32**> [#uses=1]
-; CHECK: define i32* @c1(i32* readnone %q)
+; CHECK: define i32* @c1(i32* readnone returned %q)
define i32* @c1(i32* %q) {
ret i32* %q
}
@@ -140,7 +140,7 @@ define void @test1_1(i8* %x1_1, i8* %y1_
ret void
}
-; CHECK: define i8* @test1_2(i8* nocapture readnone %x1_2, i8* %y1_2)
+; CHECK: define i8* @test1_2(i8* nocapture readnone %x1_2, i8* returned %y1_2)
define i8* @test1_2(i8* %x1_2, i8* %y1_2) {
call void @test1_1(i8* %x1_2, i8* %y1_2)
store i32* null, i32** @g
@@ -168,7 +168,7 @@ define void @test4_1(i8* %x4_1) {
ret void
}
-; CHECK: define i8* @test4_2(i8* nocapture readnone %x4_2, i8* readnone %y4_2, i8* nocapture readnone %z4_2)
+; CHECK: define i8* @test4_2(i8* nocapture readnone %x4_2, i8* readnone returned %y4_2, i8* nocapture readnone %z4_2)
define i8* @test4_2(i8* %x4_2, i8* %y4_2, i8* %z4_2) {
call void @test4_1(i8* null)
store i32* null, i32** @g
Modified: llvm/trunk/test/Transforms/FunctionAttrs/readattrs.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/FunctionAttrs/readattrs.ll?rev=276008&r1=276007&r2=276008&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/FunctionAttrs/readattrs.ll (original)
+++ llvm/trunk/test/Transforms/FunctionAttrs/readattrs.ll Tue Jul 19 13:50:26 2016
@@ -11,7 +11,7 @@ define void @test1_2(i8* %x1_2, i8* %y1_
ret void
}
-; CHECK: define i8* @test2(i8* readnone %p)
+; CHECK: define i8* @test2(i8* readnone returned %p)
define i8* @test2(i8* %p) {
store i32 0, i32* @x
ret i8* %p
@@ -53,7 +53,7 @@ define void @test7_1(i32* inalloca %a) {
ret void
}
-; CHECK: define i32* @test8_1(i32* readnone %p)
+; CHECK: define i32* @test8_1(i32* readnone returned %p)
define i32* @test8_1(i32* %p) {
entry:
ret i32* %p
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