Merging r302416:

tstellar · tstellar · commit e867bfca1a09 · 2017-05-24T14:08:01.000Z
------------------------------------------------------------------------ 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
diff --git a/include/llvm/MC/ConstantPools.h b/include/llvm/MC/ConstantPools.h
@@ -60,6 +60,8 @@ class ConstantPool {
 
   // 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
@@ -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
@@ -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
@@ -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

Original file line number	Diff line number	Diff line change
`@@ -33,6 +33,7 @@ const MCExpr ARMTargetStreamer::addConstantPoolEntry(const MCExpr Expr, SMLoc`
`33`	`33`
`34`	`34`	`void ARMTargetStreamer::emitCurrentConstantPool() {`
`35`	`35`	`ConstantPools->emitForCurrentSection(Streamer);`
	`36`	`+ ConstantPools->clearCacheForCurrentSection(Streamer);`
`36`	`37`	`}`
`37`	`38`
`38`	`39`	`// finish() - write out any non-empty assembler constant pools.`