From e867bfca1a093353e3176f875081ec29f1c9017b Mon Sep 17 00:00:00 2001
From: Tom Stellard <tstellar@redhat.com>
Date: Wed, 24 May 2017 14:08:01 +0000
Subject: [PATCH] Merging r302416:

------------------------------------------------------------------------
r302416 | mstorsjo | 2017-05-08 06:26:24 -0400 (Mon, 08 May 2017) | 19 lines

[ARM] Clear the constant pool cache on explicit .ltorg directives

Multiple ldr pseudoinstructions with the same constant value will
reuse the same constant pool entry. However, if the constant pool
is explicitly flushed with a .ltorg directive, we should not try
to reference constants in the previous pool any longer, since they
may be out of range.

This fixes assembling hand-written assembler source which repeatedly
loads the same constant value, across a binary size larger than the
pc-relative fixup range for ldr instructions (4096 bytes). Such
assembler source already uses explicit .ltorg instructions to emit
constant pools with regular intervals. However if we try to reuse
constants emitted in earlier pools, they end up out of range.

This makes the output of the testcase match what binutils gas does
(prior to this patch, it would fail to assemble).

Differential Revision: https://reviews.llvm.org/D32847
------------------------------------------------------------------------

git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_40@303746 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/llvm/MC/ConstantPools.h               |  3 +++
 lib/MC/ConstantPools.cpp                      | 11 ++++++++
 .../ARM/MCTargetDesc/ARMTargetStreamer.cpp    |  1 +
 test/MC/ARM/ltorg-range.s                     | 27 +++++++++++++++++++
 4 files changed, 42 insertions(+)
 create mode 100644 test/MC/ARM/ltorg-range.s

diff --git a/include/llvm/MC/ConstantPools.h b/include/llvm/MC/ConstantPools.h
index f0c445dbe59..39258003b3b 100644
--- a/include/llvm/MC/ConstantPools.h
+++ b/include/llvm/MC/ConstantPools.h
@@ -60,6 +60,8 @@ public:
 
   // Return true if the constant pool is empty
   bool empty();
+
+  void clearCache();
 };
 
 class AssemblerConstantPools {
@@ -83,6 +85,7 @@ class AssemblerConstantPools {
 public:
   void emitAll(MCStreamer &Streamer);
   void emitForCurrentSection(MCStreamer &Streamer);
+  void clearCacheForCurrentSection(MCStreamer &Streamer);
   const MCExpr *addEntry(MCStreamer &Streamer, const MCExpr *Expr,
                          unsigned Size, SMLoc Loc);
 
diff --git a/lib/MC/ConstantPools.cpp b/lib/MC/ConstantPools.cpp
index 9608c2c656b..bf2c39ef712 100644
--- a/lib/MC/ConstantPools.cpp
+++ b/lib/MC/ConstantPools.cpp
@@ -54,6 +54,10 @@ const MCExpr *ConstantPool::addEntry(const MCExpr *Value, MCContext &Context,
 
 bool ConstantPool::empty() { return Entries.empty(); }
 
+void ConstantPool::clearCache() {
+  CachedEntries.clear();
+}
+
 //
 // AssemblerConstantPools implementation
 //
@@ -95,6 +99,13 @@ void AssemblerConstantPools::emitForCurrentSection(MCStreamer &Streamer) {
   }
 }
 
+void AssemblerConstantPools::clearCacheForCurrentSection(MCStreamer &Streamer) {
+  MCSection *Section = Streamer.getCurrentSectionOnly();
+  if (ConstantPool *CP = getConstantPool(Section)) {
+    CP->clearCache();
+  }
+}
+
 const MCExpr *AssemblerConstantPools::addEntry(MCStreamer &Streamer,
                                                const MCExpr *Expr,
                                                unsigned Size, SMLoc Loc) {
diff --git a/lib/Target/ARM/MCTargetDesc/ARMTargetStreamer.cpp b/lib/Target/ARM/MCTargetDesc/ARMTargetStreamer.cpp
index c0d10c89635..e49f1a30674 100644
--- a/lib/Target/ARM/MCTargetDesc/ARMTargetStreamer.cpp
+++ b/lib/Target/ARM/MCTargetDesc/ARMTargetStreamer.cpp
@@ -33,6 +33,7 @@ const MCExpr *ARMTargetStreamer::addConstantPoolEntry(const MCExpr *Expr, SMLoc
 
 void ARMTargetStreamer::emitCurrentConstantPool() {
   ConstantPools->emitForCurrentSection(Streamer);
+  ConstantPools->clearCacheForCurrentSection(Streamer);
 }
 
 // finish() - write out any non-empty assembler constant pools.
diff --git a/test/MC/ARM/ltorg-range.s b/test/MC/ARM/ltorg-range.s
new file mode 100644
index 00000000000..5c27d4cd0df
--- /dev/null
+++ b/test/MC/ARM/ltorg-range.s
@@ -0,0 +1,27 @@
+@ RUN: llvm-mc -triple armv7-unknown-linux-gnueabi -filetype obj -o - %s \
+@ RUN:   | llvm-objdump -d - | FileCheck %s
+
+        ldr r0, =0x01020304
+@ CHECK: ldr
+        .ltorg
+@ CHECK: 0x01020304
+        ldr r0, =0x01020304
+        ldr r0, =0x01020304
+        ldr r0, =0x01020304
+@ CHECK: ldr
+@ CHECK: ldr
+@ CHECK: ldr
+        .ltorg
+@ CHECK: 0x01020304
+    .rep 1028
+        .word 0
+    .endr
+@ CHECK: 0x00000000
+
+        ldr r0, =0x01020304
+@ CHECK: ldr
+        .ltorg
+@ CHECK: 0x01020304
+    .rep 1028
+        .word 0
+    .endr
-- 
2.49.0