[llvm] [M68k] add 32 bit branch instrs and allow x20 and later CPUs to relax… (PR #117371)
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Fri Nov 22 12:20:13 PST 2024
https://github.com/knickish created https://github.com/llvm/llvm-project/pull/117371
… to 32 bit versions
>From 999119d15d3d920dcc84af270c7793ae33bcf00f Mon Sep 17 00:00:00 2001
From: kirk <knickish at gmail.com>
Date: Fri, 22 Nov 2024 20:16:53 +0000
Subject: [PATCH] [M68k] add 32 bit branch instrs and allow x20 and later CPUs
to relax to 32 bit versions
---
llvm/lib/Target/M68k/M68kInstrControl.td | 14 +++++
.../M68k/MCTargetDesc/M68kAsmBackend.cpp | 53 ++++++++++++++++---
llvm/test/MC/M68k/Relaxations/branch32.s | 11 ++++
3 files changed, 72 insertions(+), 6 deletions(-)
create mode 100644 llvm/test/MC/M68k/Relaxations/branch32.s
diff --git a/llvm/lib/Target/M68k/M68kInstrControl.td b/llvm/lib/Target/M68k/M68kInstrControl.td
index 6e116d7cfe4019..0c895484433643 100644
--- a/llvm/lib/Target/M68k/M68kInstrControl.td
+++ b/llvm/lib/Target/M68k/M68kInstrControl.td
@@ -190,6 +190,12 @@ foreach cc = [ "cc", "ls", "lt", "eq", "mi", "ne", "ge",
def B#cc#"16"
: MxBcc<cc, MxBrTarget16, (descend 0b0000, 0b0000),
(operand "$dst", 16, (encoder "encodePCRelImm<16>"))>;
+
+ let Predicates = [AtLeastM68020] in {
+ def B#cc#"32"
+ : MxBcc<cc, MxBrTarget32, (descend 0b1111, 0b1111),
+ (operand "$dst", 16, (encoder "encodePCRelImm<32>"))>;
+ } // AtLeastM68020
}
foreach cc = [ "cc", "ls", "lt", "eq", "mi", "ne", "ge",
@@ -223,6 +229,12 @@ def BRA8 : MxBra<MxBrTarget8,
def BRA16 : MxBra<MxBrTarget16, (descend 0b0000, 0b0000),
(operand "$dst", 16, (encoder "encodePCRelImm<16>"))>;
+let Predicates = [AtLeastM68020] in {
+def BRA32 : MxBra<MxBrTarget16, (descend 0b1111, 0b1111),
+ (operand "$dst", 32, (encoder "encodePCRelImm<32>"),
+ (decoder "DecodeImm32"))>;
+} // AtLeastM68020
+
def : Pat<(br bb:$target), (BRA8 MxBrTarget8:$target)>;
/// -------------------------------------------------
@@ -250,9 +262,11 @@ def BSR8 : MxBsr<MxBrTarget8, MxType8,
def BSR16 : MxBsr<MxBrTarget16, MxType16, (descend 0b0000, 0b0000),
(operand "$dst", 16, (encoder "encodePCRelImm<16>"))>;
+let Predicates = [AtLeastM68020] in {
def BSR32 : MxBsr<MxBrTarget32, MxType32, (descend 0b1111, 0b1111),
(operand "$dst", 32, (encoder "encodePCRelImm<32>"),
(decoder "DecodeImm32"))>;
+} // AtLeastM68020
//===----------------------------------------------------------------------===//
// Call
diff --git a/llvm/lib/Target/M68k/MCTargetDesc/M68kAsmBackend.cpp b/llvm/lib/Target/M68k/MCTargetDesc/M68kAsmBackend.cpp
index 2c52fe07bb1119..56a18534fde05b 100644
--- a/llvm/lib/Target/M68k/MCTargetDesc/M68kAsmBackend.cpp
+++ b/llvm/lib/Target/M68k/MCTargetDesc/M68kAsmBackend.cpp
@@ -39,9 +39,14 @@ using namespace llvm;
namespace {
class M68kAsmBackend : public MCAsmBackend {
+ bool Allows32BitBranch;
public:
- M68kAsmBackend(const Target &T) : MCAsmBackend(llvm::endianness::big) {}
+ M68kAsmBackend(const Target &T, const MCSubtargetInfo &STI)
+ : MCAsmBackend(llvm::endianness::big),
+ Allows32BitBranch(llvm::StringSwitch<bool>(STI.getCPU())
+ .CasesLower("m68020", "m68030", "m68040", true)
+ .Default(false)) {}
unsigned getNumFixupKinds() const override { return 0; }
@@ -129,6 +134,36 @@ static unsigned getRelaxedOpcodeBranch(const MCInst &Inst) {
return M68k::Ble16;
case M68k::Bvs8:
return M68k::Bvs16;
+ case M68k::BRA16:
+ return M68k::BRA32;
+ case M68k::Bcc16:
+ return M68k::Bcc32;
+ case M68k::Bls16:
+ return M68k::Bls32;
+ case M68k::Blt16:
+ return M68k::Blt32;
+ case M68k::Beq16:
+ return M68k::Beq32;
+ case M68k::Bmi16:
+ return M68k::Bmi32;
+ case M68k::Bne16:
+ return M68k::Bne32;
+ case M68k::Bge16:
+ return M68k::Bge32;
+ case M68k::Bcs16:
+ return M68k::Bcs32;
+ case M68k::Bpl16:
+ return M68k::Bpl32;
+ case M68k::Bgt16:
+ return M68k::Bgt32;
+ case M68k::Bhi16:
+ return M68k::Bhi32;
+ case M68k::Bvc16:
+ return M68k::Bvc32;
+ case M68k::Ble16:
+ return M68k::Ble32;
+ case M68k::Bvs16:
+ return M68k::Bvs32;
}
}
@@ -168,7 +203,7 @@ bool M68kAsmBackend::mayNeedRelaxation(const MCInst &Inst,
bool M68kAsmBackend::fixupNeedsRelaxation(const MCFixup &Fixup,
uint64_t Value) const {
// TODO Newer CPU can use 32 bit offsets, so check for this when ready
- if (!isInt<16>(Value)) {
+ if (!isInt<32>(Value) || (!Allows32BitBranch && !isInt<16>(Value))) {
llvm_unreachable("Cannot relax the instruction, value does not fit");
}
// Relax if the value is too big for a (signed) i8. This means that byte-wide
@@ -178,7 +213,13 @@ bool M68kAsmBackend::fixupNeedsRelaxation(const MCFixup &Fixup,
// A branch to the immediately following instruction automatically
// uses the 16-bit displacement format because the 8-bit
// displacement field contains $00 (zero offset).
- return Value == 0 || !isInt<8>(Value);
+ unsigned int KindLog2Size = getFixupKindLog2Size(Fixup.getKind());
+ bool FixupFieldTooSmall = false;
+ if (!isInt<8>(Value) && KindLog2Size == 0)
+ FixupFieldTooSmall |= true;
+ if (!isInt<16>(Value) && KindLog2Size <= 1)
+ FixupFieldTooSmall |= true;
+ return Value == 0 || FixupFieldTooSmall;
}
// NOTE Can tblgen help at all here to verify there aren't other instructions
@@ -218,8 +259,8 @@ namespace {
class M68kELFAsmBackend : public M68kAsmBackend {
public:
uint8_t OSABI;
- M68kELFAsmBackend(const Target &T, uint8_t OSABI)
- : M68kAsmBackend(T), OSABI(OSABI) {}
+ M68kELFAsmBackend(const Target &T, const MCSubtargetInfo &STI, uint8_t OSABI)
+ : M68kAsmBackend(T, STI), OSABI(OSABI) {}
std::unique_ptr<MCObjectTargetWriter>
createObjectTargetWriter() const override {
@@ -235,5 +276,5 @@ MCAsmBackend *llvm::createM68kAsmBackend(const Target &T,
const MCTargetOptions &Options) {
const Triple &TheTriple = STI.getTargetTriple();
uint8_t OSABI = MCELFObjectTargetWriter::getOSABI(TheTriple.getOS());
- return new M68kELFAsmBackend(T, OSABI);
+ return new M68kELFAsmBackend(T, STI, OSABI);
}
diff --git a/llvm/test/MC/M68k/Relaxations/branch32.s b/llvm/test/MC/M68k/Relaxations/branch32.s
new file mode 100644
index 00000000000000..4d92fe1001cc37
--- /dev/null
+++ b/llvm/test/MC/M68k/Relaxations/branch32.s
@@ -0,0 +1,11 @@
+; RUN: llvm-mc -triple=m68k --mcpu=m68020 -motorola-integers -filetype=obj < %s \
+; RUN: | llvm-objdump -d - | FileCheck %s
+
+; CHECK-LABEL: <RELAXED_32>:
+RELAXED_32:
+ ; CHECK: bra $ff
+ bra .LBB3_1
+ .space 0x20000 ; Greater than u16::MAX.
+.LBB3_1:
+ add.l #0, %d0
+ rts
\ No newline at end of file
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