<div dir="ltr"><br><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Jan 31, 2017 at 5:01 PM, Davide Italiano via llvm-commits <span dir="ltr"><<a href="mailto:llvm-commits@lists.llvm.org" target="_blank">llvm-commits@lists.llvm.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Author: davide<br>
Date: Tue Jan 31 19:01:22 2017<br>
New Revision: 293727<br>
<br>
URL: <a href="http://llvm.org/viewvc/llvm-project?rev=293727&view=rev" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-<wbr>project?rev=293727&view=rev</a><br>
Log:<br>
[IPSCCP] Teach how to not propagate return values of naked functions.<br>
<br>
Differential Revision: <a href="https://reviews.llvm.org/D29360" rel="noreferrer" target="_blank">https://reviews.llvm.org/<wbr>D29360</a><br>
<br>
Added:<br>
llvm/trunk/test/Transforms/<wbr>IPConstantProp/naked-return.ll<br>
Modified:<br>
llvm/trunk/lib/Transforms/<wbr>Scalar/SCCP.cpp<br>
<br>
Modified: llvm/trunk/lib/Transforms/<wbr>Scalar/SCCP.cpp<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/SCCP.cpp?rev=293727&r1=293726&r2=293727&view=diff" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-<wbr>project/llvm/trunk/lib/<wbr>Transforms/Scalar/SCCP.cpp?<wbr>rev=293727&r1=293726&r2=<wbr>293727&view=diff</a><br>
==============================<wbr>==============================<wbr>==================<br>
--- llvm/trunk/lib/Transforms/<wbr>Scalar/SCCP.cpp (original)<br>
+++ llvm/trunk/lib/Transforms/<wbr>Scalar/SCCP.cpp Tue Jan 31 19:01:22 2017<br>
@@ -1712,7 +1712,10 @@ static bool runIPSCCP(Module &M, const D<br>
<br>
// If this is an exact definition of this function, then we can propagate<br>
// information about its result into callsites of it.<br>
- if (F.hasExactDefinition())<br>
+ // Don't touch naked functions. They may contain asm returning a<br>
+ // value we don't see, so we may end up interprocedurally propagating<br>
+ // the return value incorrectly.<br>
+ if (F.hasExactDefinition() && !F.hasFnAttribute(Attribute::<wbr>Naked))<br>
Solver.AddTrackedFunction(&F);<br>
<br>
// If this function only has direct calls that we can see, we can track its<br>
<br>
Added: llvm/trunk/test/Transforms/<wbr>IPConstantProp/naked-return.ll<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/IPConstantProp/naked-return.ll?rev=293727&view=auto" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-<wbr>project/llvm/trunk/test/<wbr>Transforms/IPConstantProp/<wbr>naked-return.ll?rev=293727&<wbr>view=auto</a><br>
==============================<wbr>==============================<wbr>==================<br>
--- llvm/trunk/test/Transforms/<wbr>IPConstantProp/naked-return.ll (added)<br>
+++ llvm/trunk/test/Transforms/<wbr>IPConstantProp/naked-return.ll Tue Jan 31 19:01:22 2017<br>
@@ -0,0 +1,28 @@<br>
+; RUN: opt -ipsccp -S %s | FileCheck %s<br>
+<br>
+target datalayout = "e-m:x-p:32:32-i64:64-f80:32-<wbr>n8:16:32-a:0:32-S32"<br>
+target triple = "i686-pc-windows-msvc19.0.<wbr>24215"<br>
+<br>
+define i32 @dipsy(i32, i32) local_unnamed_addr #0 {<br>
+BasicBlock0:<br>
+ call void asm "\0D\0Apushl %ebp\0D\0Amovl 8(%esp),%eax\0D\0Amovl 12(%esp), %ebp\0D\0Acalll *%eax\0D\0Apopl %ebp\0D\0Aretl\0D\0A", ""()<br>
+ ret i32 0<br></blockquote><div><br></div><div>If this asm is going to return, shouldn't we have `unreachable` instead of `ret i32 0`? That would naturally be correct I think without requiring special handling for naked functions. I.e., the verifier should ensure that naked functions always end with `unreachable`.</div><div><br></div><div>-- Sean Silva</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
+}<br>
+<br>
+define void @tinkywinky(i32, i32, i32) local_unnamed_addr #0 {<br>
+BasicBlock1:<br>
+ call void asm "\0D\0A movl 12(%esp), %ebp\0D\0A movl 4(%esp), %eax\0D\0A movl 8(%esp), %esp\0D\0A jmpl *%eax\0D\0A", ""()<br>
+ ret void<br>
+}<br>
+<br>
+define void @patatino(i32, i32, i32) local_unnamed_addr #1 {<br>
+bb:<br>
+ %3 = tail call i32 @dipsy(i32 %0, i32 %1) #0<br>
+; Check that we don't accidentally propagate zero.<br>
+; CHECK: @tinkywinky(i32 %3, i32 %2, i32 %1) #0<br>
+ tail call void @tinkywinky(i32 %3, i32 %2, i32 %1) #0<br>
+ ret void<br>
+}<br>
+<br>
+attributes #0 = { naked noinline optnone }<br>
+attributes #1 = { "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-<wbr>leaf" }<br>
<br>
<br>
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</blockquote></div><br></div></div>