Commit 7f150d5d authored by Tom Stellard's avatar Tom Stellard
Browse files

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
------------------------------------------------------------------------

llvm-svn: 303746
parent f6a7d32d

llvm/include/llvm/MC/ConstantPools.h

+3 −0
Original line number Diff line number Diff line
@@ -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);

llvm/lib/MC/ConstantPools.cpp

+11 −0
Original line number Diff line number Diff line
@@ -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) {

llvm/lib/Target/ARM/MCTargetDesc/ARMTargetStreamer.cpp

+1 −0
Original line number Diff line number Diff line
@@ -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.

llvm/test/MC/ARM/ltorg-range.s

0 → 100644
+27 −0
Original line number Diff line number Diff line 
@ 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