[llvm] [M68k] Introduce more MOVI cases (PR #98377)
Peter Lafreniere via llvm-commits
llvm-commits at lists.llvm.org
Wed Jul 10 13:23:14 PDT 2024
https://github.com/n8pjl created https://github.com/llvm/llvm-project/pull/98377
Add three more special cases for loading registers with immediates.
The first allows values in the range of [-255, 255] to be loaded with MOVEQ, even if the register is more than 8 bits and the sign extention is unwanted. This is done by loading the bitwise complement of the desired value, then performing a NOT instruction on the loaded register.
This special case is only used when a simple MOVEQ cannot be used, and is only used for 32 bit data registers. Address registers cannot support MOVEQ, and the two-instruction sequence is no faster or smaller than a plain MOVE instruction when loading 16 bit immediates on the 68000, and likely slower for more sophisticated microarchitectures. However, the instruction sequence is both smaller and faster than the corresponding MOVE instruction for 32 bit register widths.
The second special case is for zeroing address registers. This simply expands to subtracting a register with itself, consuming one instruction word rather than 2-3, with a small improvement in speed as well.
The last special case is for assigning sign-extended 16-bit values to a full address register. This takes advantage of the fact that the movea.w instruction sign extends the output, permitting the immediate to be smaller. This is similar to using lea with a 16-bit address, which is not added in this patch as 16-bit absolute addressing is not yet implemented.
This is a v2 submission of #90817. It also creates a 'Data' test directory to better align with the backend's tablegen layout.
>From 64ffddaa84325bebd994c3b3f91f39184843e78d Mon Sep 17 00:00:00 2001
From: Peter Lafreniere <peter at n8pjl.ca>
Date: Wed, 10 Jul 2024 15:45:09 -0400
Subject: [PATCH] [M68k] Introduce more MOVI cases
Add three more special cases for loading registers with immediates.
The first allows values in the range of [-255, 255] to be loaded with MOVEQ,
even if the register is more than 8 bits and the sign extention is
unwanted. This is done by loading the bitwise complement of the desired
value, then performing a NOT instruction on the loaded register.
This special case is only used when a simple MOVEQ cannot be used, and
is only used for 32 bit data registers. Address registers cannot support
MOVEQ, and the two-instruction sequence is no faster or smaller than a plain
MOVE instruction when loading 16 bit immediates on the 68000, and likely
slower for more sophisticated microarchitectures. However, the
instruction sequence is both smaller and faster than the corresponding
MOVE instruction for 32 bit register widths.
The second special case is for zeroing address registers. This simply
expands to subtracting a register with itself, consuming one instruction
word rather than 2-3, with a small improvement in speed as well.
The last special case is for assigning sign-extended 16-bit values to
a full address register. This takes advantage of the fact that the
movea.w instruction sign extends the output, permitting the immediate
to be smaller. This is similar to using lea with a 16-bit address, which
is not added in this patch as 16-bit absolute addressing is not yet
implemented.
This is a v2 submission of #90817. It also creates a 'Data' test directory
to better align with the backend's tablegen layout.
---
llvm/lib/Target/M68k/M68kInstrInfo.cpp | 62 +++++++-
llvm/test/CodeGen/M68k/Arith/add.ll | 3 +-
llvm/test/CodeGen/M68k/CConv/fastcc-call.ll | 4 +-
.../CodeGen/M68k/{ => Data}/link-unlnk.ll | 0
.../CodeGen/M68k/{ => Data}/load-extend.ll | 0
llvm/test/CodeGen/M68k/Data/load-imm.ll | 149 ++++++++++++++++++
.../CodeGen/M68k/{Arith => Data}/sext-i1.ll | 0
7 files changed, 208 insertions(+), 10 deletions(-)
rename llvm/test/CodeGen/M68k/{ => Data}/link-unlnk.ll (100%)
rename llvm/test/CodeGen/M68k/{ => Data}/load-extend.ll (100%)
create mode 100644 llvm/test/CodeGen/M68k/Data/load-imm.ll
rename llvm/test/CodeGen/M68k/{Arith => Data}/sext-i1.ll (100%)
diff --git a/llvm/lib/Target/M68k/M68kInstrInfo.cpp b/llvm/lib/Target/M68k/M68kInstrInfo.cpp
index 338db45782c96..e0cee3ec1b48b 100644
--- a/llvm/lib/Target/M68k/M68kInstrInfo.cpp
+++ b/llvm/lib/Target/M68k/M68kInstrInfo.cpp
@@ -346,8 +346,8 @@ void M68kInstrInfo::AddZExt(MachineBasicBlock &MBB,
BuildMI(MBB, I, DL, get(And), Reg).addReg(Reg).addImm(Mask);
}
-// Convert MOVI to MOVQ if the target is a data register and the immediate
-// fits in a sign-extended i8, otherwise emit a plain MOV.
+// Convert MOVI to the appropriate instruction (sequence) for setting
+// the register to an immediate value.
bool M68kInstrInfo::ExpandMOVI(MachineInstrBuilder &MIB, MVT MVTSize) const {
Register Reg = MIB->getOperand(0).getReg();
int64_t Imm = MIB->getOperand(1).getImm();
@@ -360,18 +360,66 @@ bool M68kInstrInfo::ExpandMOVI(MachineInstrBuilder &MIB, MVT MVTSize) const {
if (AR16->contains(Reg) || AR32->contains(Reg))
IsAddressReg = true;
+ // We need to assign to the full register to make IV happy
+ Register SReg =
+ MVTSize == MVT::i32
+ ? Reg
+ : Register(RI.getMatchingMegaReg(Reg, IsAddressReg ? AR32 : DR32));
+ assert(SReg && "No viable MEGA register available");
+
LLVM_DEBUG(dbgs() << "Expand " << *MIB.getInstr() << " to ");
+ // Sign extention doesn't matter if we only use the bottom 8 bits
if (MVTSize == MVT::i8 || (!IsAddressReg && Imm >= -128 && Imm <= 127)) {
LLVM_DEBUG(dbgs() << "MOVEQ\n");
- // We need to assign to the full register to make IV happy
- Register SReg =
- MVTSize == MVT::i32 ? Reg : Register(RI.getMatchingMegaReg(Reg, DR32));
- assert(SReg && "No viable MEGA register available");
-
MIB->setDesc(get(M68k::MOVQ));
MIB->getOperand(0).setReg(SReg);
+
+ // Counter the effects of sign-extension with a bitwise not.
+ // This is only faster and smaller for 32 bit values.
+ } else if (DR32->contains(Reg) && std::abs(Imm) <= 255) {
+ LLVM_DEBUG(dbgs() << "MOVEQ and NOT\n");
+
+ MachineBasicBlock &MBB = *MIB->getParent();
+ DebugLoc DL = MIB->getDebugLoc();
+
+ Register SubReg = Register(RI.getSubReg(Reg, M68k::MxSubRegIndex8Lo));
+ assert(SubReg.id() && "No viable SUB register available");
+
+ BuildMI(MBB, MIB.getInstr(), DL, get(M68k::MOVQ), SReg).addImm(~Imm & 0xFF);
+ BuildMI(MBB, MIB.getInstr(), DL, get(M68k::NOT8d), SubReg).addReg(SubReg);
+
+ MIB->removeFromParent();
+
+ // Special case for setting address register to NULL (0)
+ } else if (IsAddressReg && Imm == 0) {
+ LLVM_DEBUG(dbgs() << "SUBA\n");
+
+ MachineBasicBlock &MBB = *MIB->getParent();
+ DebugLoc DL = MIB->getDebugLoc();
+
+ BuildMI(MBB, MIB.getInstr(), DL, get(M68k::SUB32ar), SReg)
+ .addReg(SReg, RegState::Undef)
+ .addReg(SReg, RegState::Undef);
+
+ MIB->removeFromParent();
+
+ // movea.w implicitly sign extends to the full register width,
+ // so exploit that if the immediate fits in the correct range.
+ //
+ // TODO: use lea imm.w, %an for further constants when 16-bit
+ // absolute addressing is implemented.
+ } else if (AR32->contains(Reg) && Imm >= -32768 && Imm <= 32767) {
+ LLVM_DEBUG(dbgs() << "MOVEA w/ implicit extend\n");
+
+ Register SubReg = Register(RI.getSubReg(Reg, M68k::MxSubRegIndex16Lo));
+ assert(SubReg.id() && "No viable SUB register available");
+
+ MIB->setDesc(get(M68k::MOV16ai));
+ MIB->getOperand(0).setReg(SubReg);
+
+ // Fall back to a move with immediate
} else {
LLVM_DEBUG(dbgs() << "MOVE\n");
MIB->setDesc(get(MVTSize == MVT::i16 ? M68k::MOV16ri : M68k::MOV32ri));
diff --git a/llvm/test/CodeGen/M68k/Arith/add.ll b/llvm/test/CodeGen/M68k/Arith/add.ll
index a9eb0bb815b08..417fe8f068479 100644
--- a/llvm/test/CodeGen/M68k/Arith/add.ll
+++ b/llvm/test/CodeGen/M68k/Arith/add.ll
@@ -65,7 +65,8 @@ define fastcc void @test4(ptr inreg %a) nounwind {
; CHECK-NEXT: movem.l %d2, (0,%sp) ; 8-byte Folded Spill
; CHECK-NEXT: move.l (%a0), %d0
; CHECK-NEXT: moveq #0, %d1
-; CHECK-NEXT: move.l #128, %d2
+; CHECK-NEXT: moveq #127, %d2
+; CHECK-NEXT: not.b %d2
; CHECK-NEXT: add.l (4,%a0), %d2
; CHECK-NEXT: addx.l %d0, %d1
; CHECK-NEXT: move.l %d2, (4,%a0)
diff --git a/llvm/test/CodeGen/M68k/CConv/fastcc-call.ll b/llvm/test/CodeGen/M68k/CConv/fastcc-call.ll
index 8d40ebd5228fc..f67280cf4f5d5 100644
--- a/llvm/test/CodeGen/M68k/CConv/fastcc-call.ll
+++ b/llvm/test/CodeGen/M68k/CConv/fastcc-call.ll
@@ -13,8 +13,8 @@ define i32 @foo1() nounwind uwtable {
; CHECK-NEXT: move.l #5, (%sp)
; CHECK-NEXT: moveq #1, %d0
; CHECK-NEXT: moveq #2, %d1
-; CHECK-NEXT: move.l #3, %a0
-; CHECK-NEXT: move.l #4, %a1
+; CHECK-NEXT: move.w #3, %a0
+; CHECK-NEXT: move.w #4, %a1
; CHECK-NEXT: jsr (bar1 at PLT,%pc)
; CHECK-NEXT: moveq #0, %d0
; CHECK-NEXT: adda.l #4, %sp
diff --git a/llvm/test/CodeGen/M68k/link-unlnk.ll b/llvm/test/CodeGen/M68k/Data/link-unlnk.ll
similarity index 100%
rename from llvm/test/CodeGen/M68k/link-unlnk.ll
rename to llvm/test/CodeGen/M68k/Data/link-unlnk.ll
diff --git a/llvm/test/CodeGen/M68k/load-extend.ll b/llvm/test/CodeGen/M68k/Data/load-extend.ll
similarity index 100%
rename from llvm/test/CodeGen/M68k/load-extend.ll
rename to llvm/test/CodeGen/M68k/Data/load-extend.ll
diff --git a/llvm/test/CodeGen/M68k/Data/load-imm.ll b/llvm/test/CodeGen/M68k/Data/load-imm.ll
new file mode 100644
index 0000000000000..5105e5573b0c1
--- /dev/null
+++ b/llvm/test/CodeGen/M68k/Data/load-imm.ll
@@ -0,0 +1,149 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 2
+; RUN: llc < %s -mtriple=m68k-linux -verify-machineinstrs | FileCheck %s
+
+define i1 @return_true() {
+; CHECK-LABEL: return_true:
+; CHECK: .cfi_startproc
+; CHECK-NEXT: ; %bb.0:
+; CHECK-NEXT: moveq #1, %d0
+; CHECK-NEXT: rts
+ ret i1 true
+}
+
+define i8 @return_0_i8() {
+; CHECK-LABEL: return_0_i8:
+; CHECK: .cfi_startproc
+; CHECK-NEXT: ; %bb.0:
+; CHECK-NEXT: moveq #0, %d0
+; CHECK-NEXT: rts
+ ret i8 0
+}
+
+define i16 @return_0_i16() {
+; CHECK-LABEL: return_0_i16:
+; CHECK: .cfi_startproc
+; CHECK-NEXT: ; %bb.0:
+; CHECK-NEXT: moveq #0, %d0
+; CHECK-NEXT: rts
+ ret i16 0
+}
+
+define i32 @return_0_i32() {
+; CHECK-LABEL: return_0_i32:
+; CHECK: .cfi_startproc
+; CHECK-NEXT: ; %bb.0:
+; CHECK-NEXT: moveq #0, %d0
+; CHECK-NEXT: rts
+ ret i32 0
+}
+
+define i64 @return_0_i64() {
+; CHECK-LABEL: return_0_i64:
+; CHECK: .cfi_startproc
+; CHECK-NEXT: ; %bb.0:
+; CHECK-NEXT: moveq #0, %d0
+; CHECK-NEXT: move.l %d0, %d1
+; CHECK-NEXT: rts
+ ret i64 0
+}
+
+define i16 @return_neg1_i16() {
+; CHECK-LABEL: return_neg1_i16:
+; CHECK: .cfi_startproc
+; CHECK-NEXT: ; %bb.0:
+; CHECK-NEXT: moveq #-1, %d0
+; CHECK-NEXT: rts
+ ret i16 -1
+}
+
+define i32 @return_neg1_i32() {
+; CHECK-LABEL: return_neg1_i32:
+; CHECK: .cfi_startproc
+; CHECK-NEXT: ; %bb.0:
+; CHECK-NEXT: moveq #-1, %d0
+; CHECK-NEXT: rts
+ ret i32 -1
+}
+
+define i8 @return_160_i8() {
+; CHECK-LABEL: return_160_i8:
+; CHECK: .cfi_startproc
+; CHECK-NEXT: ; %bb.0:
+; CHECK-NEXT: moveq #-96, %d0
+; CHECK-NEXT: rts
+ ret i8 160
+}
+
+define i16 @return_160_i16() {
+; CHECK-LABEL: return_160_i16:
+; CHECK: .cfi_startproc
+; CHECK-NEXT: ; %bb.0:
+; CHECK-NEXT: move.w #160, %d0
+; CHECK-NEXT: rts
+ ret i16 160
+}
+
+define i32 @return_160_i32() {
+; CHECK-LABEL: return_160_i32:
+; CHECK: .cfi_startproc
+; CHECK-NEXT: ; %bb.0:
+; CHECK-NEXT: moveq #95, %d0
+; CHECK-NEXT: not.b %d0
+; CHECK-NEXT: rts
+ ret i32 160
+}
+
+define i16 @return_14281_i16() {
+; CHECK-LABEL: return_14281_i16:
+; CHECK: .cfi_startproc
+; CHECK-NEXT: ; %bb.0:
+; CHECK-NEXT: move.w #14281, %d0
+; CHECK-NEXT: rts
+ ret i16 14281
+}
+
+define i32 @return_14281_i32() {
+; CHECK-LABEL: return_14281_i32:
+; CHECK: .cfi_startproc
+; CHECK-NEXT: ; %bb.0:
+; CHECK-NEXT: move.l #14281, %d0
+; CHECK-NEXT: rts
+ ret i32 14281
+}
+
+define i64 @return_14281_i64() {
+; CHECK-LABEL: return_14281_i64:
+; CHECK: .cfi_startproc
+; CHECK-NEXT: ; %bb.0:
+; CHECK-NEXT: moveq #0, %d0
+; CHECK-NEXT: move.l #14281, %d1
+; CHECK-NEXT: rts
+ ret i64 14281
+}
+
+define ptr @return_null() {
+; CHECK-LABEL: return_null:
+; CHECK: .cfi_startproc
+; CHECK-NEXT: ; %bb.0:
+; CHECK-NEXT: suba.l %a0, %a0
+; CHECK-NEXT: rts
+ ret ptr null
+}
+
+define ptr @return_nonnull() {
+; CHECK-LABEL: return_nonnull:
+; CHECK: .cfi_startproc
+; CHECK-NEXT: ; %bb.0:
+; CHECK-NEXT: move.w #200, %a0
+; CHECK-NEXT: rts
+ ret ptr inttoptr (i32 200 to ptr)
+}
+
+define ptr @return_large_nonnull() {
+; CHECK-LABEL: return_large_nonnull:
+; CHECK: .cfi_startproc
+; CHECK-NEXT: ; %bb.0:
+; CHECK-NEXT: move.l #74281, %a0
+; CHECK-NEXT: rts
+ ret ptr inttoptr (i32 74281 to ptr)
+}
\ No newline at end of file
diff --git a/llvm/test/CodeGen/M68k/Arith/sext-i1.ll b/llvm/test/CodeGen/M68k/Data/sext-i1.ll
similarity index 100%
rename from llvm/test/CodeGen/M68k/Arith/sext-i1.ll
rename to llvm/test/CodeGen/M68k/Data/sext-i1.ll
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