Merging r293727:

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r293727 | davide | 2017-01-31 17:01:22 -0800 (Tue, 31 Jan 2017) | 3 lines

[IPSCCP] Teach how to not propagate return values of naked functions.

Differential Revision:  https://reviews.llvm.org/D29360
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llvm-svn: 293796

llvm/lib/Transforms/Scalar/SCCP.cpp

@@ -1705,7 +1705,10 @@ static bool runIPSCCP(Module &M, const DataLayout &DL,
 
     // If this is an exact definition of this function, then we can propagate
     // information about its result into callsites of it.
-    if (F.hasExactDefinition())
+    // Don't touch naked functions. They may contain asm returning a
+    // value we don't see, so we may end up interprocedurally propagating
+    // the return value incorrectly.
+    if (F.hasExactDefinition() && !F.hasFnAttribute(Attribute::Naked))
       Solver.AddTrackedFunction(&F);
 
     // If this function only has direct calls that we can see, we can track its

llvm/test/Transforms/IPConstantProp/naked-return.ll

@@ -0,0 +1,28 @@
+; RUN: opt -ipsccp -S %s | FileCheck %s
+
+target datalayout = "e-m:x-p:32:32-i64:64-f80:32-n8:16:32-a:0:32-S32"
+target triple = "i686-pc-windows-msvc19.0.24215"
+
+define i32 @dipsy(i32, i32) local_unnamed_addr #0 {
+BasicBlock0:
+  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", ""()
+  ret i32 0
+}
+
+define void @tinkywinky(i32, i32, i32) local_unnamed_addr #0 {
+BasicBlock1:
+  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", ""()
+  ret void
+}
+
+define void @patatino(i32, i32, i32) local_unnamed_addr #1 {
+bb:
+  %3 = tail call i32 @dipsy(i32 %0, i32 %1) #0
+; Check that we don't accidentally propagate zero.
+; CHECK: @tinkywinky(i32 %3, i32 %2, i32 %1) #0
+  tail call void @tinkywinky(i32 %3, i32 %2, i32 %1) #0
+  ret void
+}
+
+attributes #0 = { naked noinline optnone }
+attributes #1 = { "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" }