[RISCV] Implement Relaxations for QC.E.J/QC.E.JAL

These relaxations are like call relaxations, so they are done in the
same phase as call relaxations.

The Relaxations are:
- QC.E.J to C.J or JAL X0
- QC.E.JAL to C.JAL or JAL X1

This change also adds a command-line switch for turning off all the xqci
relaxations, which defaults to Off.

Signed-off-by: Sam Elliott <[email protected]>

Author: lenary

include/eld/Config/GeneralOptions.h

@@ -870,6 +870,10 @@ class GeneralOptions {
 
   bool getRISCVRelaxToC() const { return BRiscvRelaxToC; }
 
+  void setRISCVRelaxXqci(bool Value) { BRiscvRelaxXqci = Value; }
+
+  bool getRISCVRelaxXqci() const { return BRiscvRelaxXqci; }
+
   bool warnCommon() const { return BWarnCommon; }
 
   void setWarnCommon() { BWarnCommon = true; }
@@ -1225,6 +1229,7 @@ class GeneralOptions {
   bool RiscvZeroRelax = true;             // Zero-page relaxation
   bool RiscvGPRelax = true;               // GP relaxation
   bool BRiscvRelaxToC = true; // enable riscv relax to compressed code
+  bool BRiscvRelaxXqci = false; // enable riscv relaxations for xqci
   bool AllowIncompatibleSectionsMix = false; // Allow incompatibleSections;
   bool ProgressBar = false;                  // Show progressbar.
   bool RecordInputFiles = false;             // --reproduce

include/eld/Driver/RISCVLinkerOptions.td

@@ -41,6 +41,15 @@ def no_riscv_relax_compressed
       HelpText<"Disable relaxation to compressed instructions">,
       Group<grp_riscv_linker>;
 
+def riscv_relax_xqci
+    : Flag<["--"], "relax-xqci">,
+      HelpText<"Enable relaxing to/from Xqci instructions">,
+      Group<grp_riscv_linker>;
+def no_riscv_relax_xqci
+    : Flag<["--"], "no-relax-xqci">,
+      HelpText<"Disable relaxing to/from Xqci instructions (default behavior)">,
+      Group<grp_riscv_linker>;
+
 def riscv_relax : Flag<["--"], "relax">,
                   HelpText<"Enable relaxation (default behavior)">,
                   Group<grp_riscv_linker>;

lib/LinkerWrapper/RISCVLinkDriver.cpp

@@ -121,6 +121,11 @@ opt::OptTable *RISCVLinkDriver::parseOptions(ArrayRef<const char *> Args,
   if (ArgList.hasArg(OPT_RISCVLinkOptTable::no_riscv_relax_compressed))
     Config.options().setRISCVRelaxToC(false);
 
+  // --relax-xqci, --no-relax-xqci  (default)
+  Config.options().setRISCVRelaxXqci(
+      ArgList.hasFlag(OPT_RISCVLinkOptTable::riscv_relax_xqci,
+                      OPT_RISCVLinkOptTable::no_riscv_relax_xqci, false));
+
   // --enable-bss-mixing
   if (ArgList.hasArg(OPT_RISCVLinkOptTable::enable_bss_mixing))
     Config.options().setAllowBSSMixing(true);

lib/Target/RISCV/RISCVLDBackend.cpp

@@ -299,6 +299,75 @@ bool RISCVLDBackend::doRelaxationCall(Relocation *reloc, bool DoCompressed) {
   return true;
 }
 
+bool RISCVLDBackend::doRelaxationQCCall(Relocation *reloc, bool DoCompressed) {
+  // This function performs the relaxation to replace: QC.E.JAL or QC.E.J with
+  // one of JAL, C.J, or C.JAL.
+
+  Fragment *frag = reloc->targetRef()->frag();
+  RegionFragmentEx *region = llvm::dyn_cast<RegionFragmentEx>(frag);
+  if (!region)
+    return true;
+  uint64_t offset = reloc->targetRef()->offset();
+
+  // extract instruction
+  uint64_t qc_e_jump = reloc->target() & 0xffffffffffff;
+  bool isTailCall = (qc_e_jump & 0xf1f07f) == 0x00401f;
+
+  Relocator::DWord S = getSymbolValuePLT(*reloc);
+  Relocator::DWord A = reloc->addend();
+  Relocator::DWord P = reloc->place(m_Module);
+  Relocator::DWord X = S + A - P;
+
+  bool canRelaxXqci =
+      config().targets().is32Bits() && config().options().getRISCVRelaxXqci();
+  bool canRelax =
+      config().options().getRISCVRelax() && canRelaxXqci && llvm::isInt<21>(X);
+  bool canCompress = DoCompressed && llvm::isInt<12>(X);
+
+  if (!canRelax) {
+    reportMissedRelaxation("RISCV_QC_E_CALL", *region, offset,
+                           canCompress ? 4 : 2, reloc->symInfo()->name());
+    return false;
+  }
+
+  if (canCompress) {
+    uint32_t compressed = isTailCall ? 0xa001 : 0x2001;
+    const char *msg = isTailCall ? "RISCV_QC_E_J_C" : "RISCV_QC_E_JAL_C";
+
+    if (m_Module.getPrinter()->isVerbose())
+      config().raise(Diag::relax_to_compress)
+          << msg << llvm::utohexstr(qc_e_jump, true, 12)
+          << llvm::utohexstr(compressed, true, 4) << reloc->symInfo()->name()
+          << region->getOwningSection()->name() << llvm::utohexstr(offset)
+          << region->getOwningSection()
+                 ->getInputFile()
+                 ->getInput()
+                 ->decoratedPath();
+
+    region->replaceInstruction(offset, reloc, compressed, 2);
+    // Replace the reloc to R_RISCV_RVC_JUMP
+    reloc->setType(llvm::ELF::R_RISCV_RVC_JUMP);
+    reloc->setTargetData(compressed);
+    relaxDeleteBytes(msg, *region, offset + 2, 4,
+                     reloc->symInfo()->name());
+    return true;
+  }
+
+  // Replace the instruction to JAL
+  unsigned rd = isTailCall ? /*x0*/ 0 : /*ra*/ 1;
+  uint32_t jal_instr = 0x6fu | rd << 7;
+  region->replaceInstruction(offset, reloc, jal_instr, 4);
+  // Replace the reloc to R_RISCV_JAL
+  reloc->setType(llvm::ELF::R_RISCV_JAL);
+  reloc->setTargetData(jal_instr);
+  // Delete the next instruction
+  const char *msg = isTailCall ? "RISCV_QC_E_J" : "RISCV_QC_E_JAL";
+  relaxDeleteBytes(msg, *region, offset + 4, 2,
+                   reloc->symInfo()->name());
+
+  return true;
+}
+
 bool RISCVLDBackend::doRelaxationLui(Relocation *reloc, Relocator::DWord G) {
 
   /* Three types of relaxation can be applied here, in order of preference:
@@ -759,6 +828,11 @@ void RISCVLDBackend::mayBeRelax(int relaxation_pass, bool &pFinished) {
               pFinished = false;
           break;
         }
+        case ELF::riscv::internal::R_RISCV_QC_E_CALL_PLT: {
+          if (nextRelax && relaxation_pass == RELAXATION_CALL)
+            doRelaxationQCCall(relocation, DoCompressed);
+          break;
+        }
         }
         if (!config().getDiagEngine()->diagnose()) {
           m_Module.setFailure(true);

lib/Target/RISCV/RISCVLDBackend.h

@@ -198,6 +198,7 @@ class RISCVLDBackend : public GNULDBackend {
   bool isGOTReloc(Relocation *reloc) const;
 
   bool doRelaxationCall(Relocation *R, bool DoCompressed);
+  bool doRelaxationQCCall(Relocation *R, bool DoCompressed);
 
   bool doRelaxationLui(Relocation *R, Relocation::DWord G);
 

test/RISCV/standalone/Relaxation/QC_E_CALL_TO_JAL/Inputs/shared.s

@@ -0,0 +1,9 @@
+	.text
+	.global f
+f:
+	/* exact+relax needed while llvm/llvm-project#142702 is not yet fixed/landed */
+	.option exact
+	.option relax
+
+	qc.e.jal	f
+	qc.e.j	f

test/RISCV/standalone/Relaxation/QC_E_CALL_TO_JAL/Inputs/x.s

@@ -0,0 +1,35 @@
+	/* exact+relax needed while llvm/llvm-project#142702 is not yet fixed/landed */
+	.option exact
+	.option relax
+
+	.text
+	.align	1
+	.type	f, @function
+f:
+	ret
+	.size	f, .-f
+
+	.align	1
+	.globl	main
+	.type	main, @function
+main:
+	qc.e.jal	f
+	qc.e.j	f
+
+	.org	0x780
+	qc.e.jal	f
+	qc.e.j	f
+
+	.org	0x880
+	qc.e.jal	f
+	qc.e.j	f
+
+	.org	0xfff00
+	qc.e.jal	f
+	qc.e.j	f
+
+	.org	0x100100
+	qc.e.jal	f
+	qc.e.j	f
+
+	.size	main, .-main

test/RISCV/standalone/Relaxation/QC_E_CALL_TO_JAL/QC_E_CALL_TO_JAL.test

@@ -0,0 +1,116 @@
+#----------QC_E_CALL_TO_JAL.test----------------- Executable------------------#
+#BEGIN_COMMENT
+# Do relaxation from QC.E.J and QC.E.JAL to JAL or C.J/C.JAL
+#END_COMMENT
+#--------------------------------------------------------------------
+REQUIRES: riscv32
+RUN: %clang %clangopts -c %p/Inputs/x.s -o %t.o -menable-experimental-extensions -march=rv32gc_xqcilb0p2
+
+# Relaxations are enabled, including compressed ones.
+RUN: %link %linkopts --relax-xqci %t.o -o %t.1.out -MapStyle txt -Map %t.1.map --verbose 2>&1 | %filecheck %s --check-prefix=VERBOSE_RELAX_C
+RUN: %link %linkopts --relax-xqci %t.o -o %t.1.so -shared -MapStyle txt -Map %t.1.so.map --verbose 2>&1 | %filecheck %s --check-prefix=VERBOSE_RELAX_C
+VERBOSE_RELAX_C: RISCV_QC_E_JAL_C : relaxing instruction 0x00000000c01f to compressed instruction 0x2001 for symbol f in section .text+0x4 file {{.*}}.o
+VERBOSE_RELAX_C: RISCV_QC_E_JAL_C : Deleting 4 bytes for symbol 'f' in section .text+0x6 file {{.*}}.o
+VERBOSE_RELAX_C: RISCV_QC_E_J_C : relaxing instruction 0x00000000401f to compressed instruction 0xa001 for symbol f in section .text+0x6 file {{.*}}.o
+VERBOSE_RELAX_C: RISCV_QC_E_J_C : Deleting 4 bytes for symbol 'f' in section .text+0x8 file {{.*}}.o
+VERBOSE_RELAX_C: RISCV_QC_E_JAL_C : relaxing instruction 0x00000000c01f to compressed instruction 0x2001 for symbol f in section .text+0x778 file {{.*}}.o
+VERBOSE_RELAX_C: RISCV_QC_E_JAL_C : Deleting 4 bytes for symbol 'f' in section .text+0x77a file {{.*}}.o
+VERBOSE_RELAX_C: RISCV_QC_E_J_C : relaxing instruction 0x00000000401f to compressed instruction 0xa001 for symbol f in section .text+0x77A file {{.*}}.o
+VERBOSE_RELAX_C: RISCV_QC_E_J_C : Deleting 4 bytes for symbol 'f' in section .text+0x77c file {{.*}}.o
+VERBOSE_RELAX_C: RISCV_QC_E_JAL : Deleting 2 bytes for symbol 'f' in section .text+0x874 file {{.*}}.o
+VERBOSE_RELAX_C: RISCV_QC_E_J : Deleting 2 bytes for symbol 'f' in section .text+0x878 file {{.*}}.o
+VERBOSE_RELAX_C: RISCV_QC_E_JAL : Deleting 2 bytes for symbol 'f' in section .text+0xffef0 file {{.*}}.o
+VERBOSE_RELAX_C: RISCV_QC_E_J : Deleting 2 bytes for symbol 'f' in section .text+0xffef4 file {{.*}}.o
+VERBOSE_RELAX_C: RISCV_QC_E_CALL : Cannot relax 2 bytes for symbol 'f' in section .text+0x1000e8 file {{.*}}.o
+VERBOSE_RELAX_C: RISCV_QC_E_CALL : Cannot relax 2 bytes for symbol 'f' in section .text+0x1000ee file {{.*}}.o
+
+RUN: %objdump -d %t.1.out 2>&1 | %filecheck %s --check-prefix=DUMP_RELAX_C
+RUN: %objdump -d %t.1.so 2>&1 | %filecheck %s --check-prefix=DUMP_RELAX_C
+DUMP_RELAX_C: 3ff5        jal 0x{{[[:xdigit:]]+}} <f>
+DUMP_RELAX_C: bfed        j 0x{{[[:xdigit:]]+}} <f>
+DUMP_RELAX_C: 3061        jal 0x{{[[:xdigit:]]+}} <f>
+DUMP_RELAX_C: b059        j 0x{{[[:xdigit:]]+}} <f>
+DUMP_RELAX_C: f90ff0ef  jal 0x{{[[:xdigit:]]+}} <f>
+DUMP_RELAX_C: f8cff06f  j 0x{{[[:xdigit:]]+}} <f>
+DUMP_RELAX_C: 914000ef  jal 0x{{[[:xdigit:]]+}} <f>
+DUMP_RELAX_C: 9100006f  j 0x{{[[:xdigit:]]+}} <f>
+DUMP_RELAX_C: cc9f f00e ffef  qc.e.jal 0x{{[[:xdigit:]]+}} <f>
+DUMP_RELAX_C: 499f f00e ffef  qc.e.j 0x{{[[:xdigit:]]+}} <f>
+
+RUN: %filecheck %s --input-file=%t.1.map --check-prefix=MAP_RELAX_C
+RUN: %filecheck %s --input-file=%t.1.so.map --check-prefix=MAP_RELAX_C
+MAP_RELAX_C: # LinkStats Begin
+MAP_RELAX_C: # RelaxationBytesDeleted : 24
+MAP_RELAX_C: # RelaxationBytesMissed : 4
+MAP_RELAX_C: # LinkStats End
+
+MAP_RELAX_C: .text {{.+}}, Alignment: 0x2, Flags: SHF_ALLOC|SHF_EXECINSTR, Type: SHT_PROGBITS
+MAP_RELAX_C: # RelaxationBytesDeleted : 24
+MAP_RELAX_C: # RelaxationBytesMissed : 4
+MAP_RELAX_C: .text {{.+}}.o     #SHT_PROGBITS,SHF_ALLOC|SHF_EXECINSTR,2
+
+# Only non-compressed relaxations are enabled.
+RUN: %link %linkopts --relax-xqci --no-relax-c %t.o -o %t.2.out -MapStyle txt -Map %t.2.map --verbose 2>&1 | %filecheck %s --check-prefix=VERBOSE_RELAX
+RUN: %link %linkopts --relax-xqci --no-relax-c %t.o -o %t.2.so -shared -MapStyle txt -Map %t.2.so.map --verbose 2>&1 | %filecheck %s --check-prefix=VERBOSE_RELAX
+VERBOSE_RELAX: RISCV_QC_E_JAL : Deleting 2 bytes for symbol 'f' in section .text+0x8 file {{.*}}.o
+VERBOSE_RELAX: RISCV_QC_E_J : Deleting 2 bytes for symbol 'f' in section .text+0xc file {{.*}}.o
+VERBOSE_RELAX: RISCV_QC_E_JAL : Deleting 2 bytes for symbol 'f' in section .text+0x780 file {{.*}}.o
+VERBOSE_RELAX: RISCV_QC_E_J : Deleting 2 bytes for symbol 'f' in section .text+0x784 file {{.*}}.o
+VERBOSE_RELAX: RISCV_QC_E_JAL : Deleting 2 bytes for symbol 'f' in section .text+0x87c file {{.*}}.o
+VERBOSE_RELAX: RISCV_QC_E_J : Deleting 2 bytes for symbol 'f' in section .text+0x880 file {{.*}}.o
+VERBOSE_RELAX: RISCV_QC_E_JAL : Deleting 2 bytes for symbol 'f' in section .text+0xffef8 file {{.*}}.o
+VERBOSE_RELAX: RISCV_QC_E_J : Deleting 2 bytes for symbol 'f' in section .text+0xffefc file {{.*}}.o
+VERBOSE_RELAX: RISCV_QC_E_CALL : Cannot relax 2 bytes for symbol 'f' in section .text+0x1000f0 file {{.*}}.o
+VERBOSE_RELAX: RISCV_QC_E_CALL : Cannot relax 2 bytes for symbol 'f' in section .text+0x1000f6 file {{.*}}.o
+
+RUN: %objdump -d %t.2.out 2>&1 | %filecheck %s --check-prefix=DUMP_RELAX
+RUN: %objdump -d %t.2.so 2>&1 | %filecheck %s --check-prefix=DUMP_RELAX
+DUMP_RELAX: ffdff0ef  jal 0x{{[[:xdigit:]]+}} <f>
+DUMP_RELAX: ff9ff06f  j 0x{{[[:xdigit:]]+}} <f>
+DUMP_RELAX: 885ff0ef  jal 0x{{[[:xdigit:]]+}} <f>
+DUMP_RELAX: 881ff06f  j 0x{{[[:xdigit:]]+}} <f>
+DUMP_RELAX: f88ff0ef  jal 0x{{[[:xdigit:]]+}} <f>
+DUMP_RELAX: f84ff06f  j 0x{{[[:xdigit:]]+}} <f>
+DUMP_RELAX: 90c000ef  jal 0x{{[[:xdigit:]]+}} <f>
+DUMP_RELAX: 9080006f  j 0x{{[[:xdigit:]]+}} <f>
+DUMP_RELAX: c89f f00e ffef  qc.e.jal 0x{{[[:xdigit:]]+}} <f>
+DUMP_RELAX: 459f f00e ffef  qc.e.j 0x{{[[:xdigit:]]+}} <f>
+
+RUN: %filecheck %s --input-file=%t.2.map --check-prefix=MAP_RELAX
+RUN: %filecheck %s --input-file=%t.2.so.map --check-prefix=MAP_RELAX
+MAP_RELAX: # LinkStats Begin
+MAP_RELAX: # RelaxationBytesDeleted : 16
+MAP_RELAX: # LinkStats End
+
+MAP_RELAX: .text {{.+}}, Alignment: 0x2, Flags: SHF_ALLOC|SHF_EXECINSTR, Type: SHT_PROGBITS
+MAP_RELAX: # RelaxationBytesDeleted : 16
+MAP_RELAX: .text {{.+}}.o     #SHT_PROGBITS,SHF_ALLOC|SHF_EXECINSTR,2
+
+### Relaxations are disabled.
+RUN: %link %linkopts --no-relax-xqci --no-relax %t.o -o %t.3.out -MapStyle txt -Map %t.3.map --verbose 2>&1 | %filecheck %s --check-prefix=VERBOSE_NORELAX
+RUN: %link %linkopts --no-relax-xqci --no-relax %t.o -o %t.3.so -shared -MapStyle txt -Map %t.3.so.map --verbose 2>&1 | %filecheck %s --check-prefix=VERBOSE_NORELAX
+VERBOSE_NORELAX-COUNT-10: RISCV_QC_E_CALL : Cannot relax
+VERBOSE_NORELAX-NOT: Deleting
+
+RUN: %objdump -d %t.3.out 2>&1 | %filecheck %s --check-prefix=DUMP_NORELAX
+RUN: %objdump -d %t.3.so 2>&1 | %filecheck %s --check-prefix=DUMP_NORELAX
+DUMP_NORELAX: qc.e.jal
+DUMP_NORELAX: qc.e.j
+DUMP_NORELAX: qc.e.jal
+DUMP_NORELAX: qc.e.j
+DUMP_NORELAX: qc.e.jal
+DUMP_NORELAX: qc.e.j
+DUMP_NORELAX: qc.e.jal
+DUMP_NORELAX: qc.e.j
+DUMP_NORELAX: qc.e.jal
+DUMP_NORELAX: qc.e.j
+
+RUN: %filecheck %s --input-file=%t.3.map --check-prefix=MAP_NORELAX
+RUN: %filecheck %s --input-file=%t.3.so.map --check-prefix=MAP_NORELAX
+MAP_NORELAX: # LinkStats Begin
+MAP_NORELAX-NOT: # RelaxationBytesDeleted
+MAP_NORELAX: # LinkStats End
+
+MAP_NORELAX: .text {{.+}}, Alignment: 0x2, Flags: SHF_ALLOC|SHF_EXECINSTR, Type: SHT_PROGBITS
+MAP_NORELAX-NOT: # RelaxationBytesDeleted
+MAP_NORELAX: .text {{.+}}.o     #SHT_PROGBITS,SHF_ALLOC|SHF_EXECINSTR,2

test/RISCV/standalone/Relaxation/QC_E_CALL_TO_JAL/QC_E_CALL_TO_JAL_PLT.test

@@ -0,0 +1,14 @@
+#----------QC_E_CALL_TO_JAL_PLT.test-------------------------------#
+#BEGIN_COMMENT
+# Check that offset to PLT is used when relaxing.
+#END_COMMENT
+#--------------------------------------------------------------------
+REQUIRES: riscv32
+RUN: %clang %clangopts -c %p/Inputs/shared.s -o %t.shared.o -menable-experimental-extensions -march=rv32gc_xqcilb0p2
+RUN: %link %linkopts --relax-xqci -shared %t.shared.o -o %t.so --section-start=.text=0x1000 --section-start=.plt=0x20000
+RUN: %objdump -d %t.so 2>&1 | %filecheck %s
+
+CHECK: {{0+}}20000 <.plt>:
+CHECK: {{0+}}01000 <f>:
+    1000: 0201f0ef      jal     0x20020 <.plt+0x20>
+    1004: 01c1f06f      j       0x20020 <.plt+0x20>