[ThinLTO] Prevent exporting of locals used/defined in module level asm

Summary:
This patch uses the same approach added for inline asm in r285513 to
similarly prevent promotion/renaming of locals used or defined in module
level asm.

All static global values defined in normal IR and used in module level asm
should be included on either the llvm.used or llvm.compiler.used global.
The former were already being flagged as NoRename in the summary, and
I've simply added llvm.compiler.used values to this handling.

Module level asm may also contain defs of values. We need to prevent
export of any refs to local values defined in module level asm (e.g. a
ref in normal IR), since that also requires renaming/promotion of the
local. To do that, the summary index builder looks at all values in the
module level asm string that are not marked Weak or Global, which is
exactly the set of locals that are defined. A summary is created for
each of these local defs and flagged as NoRename.

This required adding handling to the BitcodeWriter to look at GV
declarations to see if they have a summary (rather than skipping them
all).

Finally, added an assert to IRObjectFile::CollectAsmUndefinedRefs to
ensure that an MCAsmParser is available, otherwise the module asm parse
would silently fail. Initialized the asm parser in the opt tool for use
in testing this fix.

Fixes PR30610.

Reviewers: mehdi_amini

Subscribers: johanengelen, krasin, llvm-commits

Differential Revision: https://reviews.llvm.org/D26146

llvm-svn: 286297

3 files changed, 99 insertions, 0 deletions

diff --git a/llvm/test/LTO/X86/current-section.ll b/llvm/test/LTO/X86/current-section.ll
index 49eee49ae62..69f8bfaac3b 100644
--- a/llvm/test/LTO/X86/current-section.ll
+++ b/llvm/test/LTO/X86/current-section.ll
@@ -2,4 +2,7 @@
 ; RUN: llvm-lto -o %t2 %t1
 ; REQUIRES: default_triple
 
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
 module asm ".align 4"
diff --git a/llvm/test/ThinLTO/X86/Inputs/module_asm2.ll b/llvm/test/ThinLTO/X86/Inputs/module_asm2.ll
new file mode 100644
index 00000000000..e823277da67
--- /dev/null
+++ b/llvm/test/ThinLTO/X86/Inputs/module_asm2.ll
@@ -0,0 +1,12 @@
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define i32 @main({ i64, { i64, i8* }* } %unnamed) #0 {
+  %1 = call i32 @func1() #1
+  %2 = call i32 @func2() #1
+  %3 = call i32 @func3() #1
+  ret i32 %1
+}
+declare i32 @func1() #1
+declare i32 @func2() #1
+declare i32 @func3() #1
diff --git a/llvm/test/ThinLTO/X86/module_asm2.ll b/llvm/test/ThinLTO/X86/module_asm2.ll
new file mode 100644
index 00000000000..90ef75fbc5e
--- /dev/null
+++ b/llvm/test/ThinLTO/X86/module_asm2.ll
@@ -0,0 +1,84 @@
+; Test to ensure that uses and defs in module level asm are handled
+; appropriately. Specifically, we should conservatively block importing
+; of any references to these values, as they can't be renamed.
+; RUN: opt -module-summary %s -o %t1.bc
+; RUN: opt -module-summary %p/Inputs/module_asm2.ll -o %t2.bc
+
+; RUN: llvm-lto -thinlto-action=run -exported-symbol=main -exported-symbol=func1 -exported-symbol=func2 -exported-symbol=func3 %t1.bc %t2.bc
+; RUN: llvm-nm %t1.bc.thinlto.o | FileCheck  %s --check-prefix=NM0
+; RUN: llvm-nm %t2.bc.thinlto.o | FileCheck  %s --check-prefix=NM1
+
+; RUN: llvm-lto2 %t1.bc %t2.bc -o %t.o -save-temps \
+; RUN:     -r=%t1.bc,foo,plx \
+; RUN:     -r=%t1.bc,b,pl \
+; RUN:     -r=%t1.bc,x,pl \
+; RUN:     -r=%t1.bc,func1,pl \
+; RUN:     -r=%t1.bc,func2,pl \
+; RUN:     -r=%t1.bc,func3,pl \
+; RUN:     -r=%t2.bc,main,plx \
+; RUN:     -r=%t2.bc,func1,l \
+; RUN:     -r=%t2.bc,func2,l \
+; RUN:     -r=%t2.bc,func3,l
+; RUN: llvm-nm %t.o.0 | FileCheck  %s --check-prefix=NM0
+; RUN: llvm-nm %t.o.1 | FileCheck  %s --check-prefix=NM1
+
+; Check that local values b and x, which are referenced on
+; llvm.used and llvm.compiler.used, respectively, are not promoted.
+; Similarly, foo which is defined in module level asm should not be
+; promoted.
+; NM0-DAG: d b
+; NM0-DAG: d x
+; NM0-DAG: t foo
+; NM0-DAG: T func1
+; NM0-DAG: T func2
+; NM0-DAG: T func3
+
+; Ensure that foo, b and x are likewise not exported (imported as refs
+; into the other module), since they can't be promoted. Additionally,
+; referencing functions func1, func2 and func3 should not have been
+; imported.
+; NM1-NOT: foo
+; NM1-NOT: b
+; NM1-NOT: x
+; NM1-DAG: U func1
+; NM1-DAG: U func2
+; NM1-DAG: U func3
+; NM1-DAG: T main
+; NM1-NOT: foo
+; NM1-NOT: b
+; NM1-NOT: x
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+@b = internal global i32 1, align 4
+@x = internal global i32 1, align 4
+
+@llvm.compiler.used = appending global [1 x i8*] [i8* bitcast (i32* @b to i8*)], section "llvm.metadata"
+@llvm.used = appending global [1 x i8*] [i8* bitcast (i32* @x to i8*)], section "llvm.metadata"
+
+module asm "\09.text"
+module asm "\09.type\09foo,@function"
+module asm "foo:"
+module asm "\09movl    b, %eax"
+module asm "\09movl    x, %edx"
+module asm "\09ret "
+module asm "\09.size\09foo, .-foo"
+module asm ""
+
+declare i16 @foo() #0
+
+define i32 @func1() #1 {
+  call i16 @foo()
+  ret i32 1
+}
+
+define i32 @func2() #1 {
+  %1 = load i32, i32* @b, align 4
+  ret i32 %1
+}
+
+define i32 @func3() #1 {
+  %1 = load i32, i32* @x, align 4
+  ret i32 %1
+}