[llvm] 1533591 - [AVR] Remove regalloc workaround for LDDWRdPtrQ

[Ayke van Laethem via llvm-commits]

Author: Ayke van Laethem
Date: 2022-01-23T17:08:00+01:00
New Revision: 153359180a9d5a6cea3985db5d3396218dc6252d

URL: https://github.com/llvm/llvm-project/commit/153359180a9d5a6cea3985db5d3396218dc6252d
DIFF: https://github.com/llvm/llvm-project/commit/153359180a9d5a6cea3985db5d3396218dc6252d.diff

LOG: [AVR] Remove regalloc workaround for LDDWRdPtrQ

Background: https://github.com/avr-rust/rust-legacy-fork/issues/126

In short, this workaround was introduced to fix a "ran out of registers
during regalloc" issue. The root cause has since been fixed in
https://reviews.llvm.org/D54218 so this workaround can be removed.

There is one test that changes a little bit, removing a single
instruction. I also compiled compiler-rt before and after this patch but
didn't see a difference. So presumably the impact is very low. Still,
it's nice to be able to remove such a workaround.

Differential Revision: https://reviews.llvm.org/D117831

Added: 
    

Modified: 
    llvm/lib/Target/AVR/AVRInstrInfo.td
    llvm/lib/Target/AVR/AVRRegisterInfo.td
    llvm/test/CodeGen/AVR/lpmx.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Target/AVR/AVRInstrInfo.td b/llvm/lib/Target/AVR/AVRInstrInfo.td
index a365bc868683d..5cbf3baef5466 100644
--- a/llvm/lib/Target/AVR/AVRInstrInfo.td
+++ b/llvm/lib/Target/AVR/AVRInstrInfo.td
@@ -1394,7 +1394,7 @@ let canFoldAsLoad = 1, isReMaterializable = 1 in {
   // ldd Rd,   P+q
   // ldd Rd+1, P+q+1
   let Constraints = "@earlyclobber $dst" in def LDDWRdPtrQ
-      : Pseudo<(outs DREGS_WITHOUT_YZ_WORKAROUND
+      : Pseudo<(outs DREGS
                 : $dst),
                (ins memri
                 : $memri),

diff  --git a/llvm/lib/Target/AVR/AVRRegisterInfo.td b/llvm/lib/Target/AVR/AVRRegisterInfo.td
index bb4e86ca0536f..c5fda788fe4d7 100644
--- a/llvm/lib/Target/AVR/AVRRegisterInfo.td
+++ b/llvm/lib/Target/AVR/AVRRegisterInfo.td
@@ -178,26 +178,6 @@ def DREGSMOVW : RegisterClass<"AVR", [i16], 8,
                                   R29R28, R17R16, R15R14, R13R12, R11R10, R9R8,
                                   R7R6, R5R4, R3R2, R1R0)>;
 
-// The 16-bit DREGS register class, excluding the Z pointer register.
-//
-// This is used by instructions which cause high pointer register
-// contention which leads to an assertion in the register allocator.
-//
-// There is no technical reason why instructions that use this class
-// cannot use Z; it's simply a workaround a regalloc bug.
-//
-// More information can be found in PR39553.
-def DREGS_WITHOUT_YZ_WORKAROUND
-    : RegisterClass<"AVR", [i16], 8,
-                    (
-                        // Return value and arguments.
-                        add R25R24, R19R18, R21R20, R23R22,
-                        // Scratch registers.
-                        R27R26,
-                        // Callee saved registers.
-                        R17R16, R15R14, R13R12, R11R10, R9R8, R7R6, R5R4, R3R2,
-                        R1R0)>;
-
 // 16-bit register class for immediate instructions.
 def DLDREGS : RegisterClass<"AVR", [i16], 8,
                             (

diff  --git a/llvm/test/CodeGen/AVR/lpmx.ll b/llvm/test/CodeGen/AVR/lpmx.ll
index 4a78ce705e7e5..c5162e2efb503 100644
--- a/llvm/test/CodeGen/AVR/lpmx.ll
+++ b/llvm/test/CodeGen/AVR/lpmx.ll
@@ -22,13 +22,12 @@ define i16 @foo0(i16 %a) addrspace(1) {
 ; CHECK-O0-NEXT:    out 61, r28
 ; CHECK-O0-NEXT:    std Y+1, r24
 ; CHECK-O0-NEXT:    std Y+2, r25
-; CHECK-O0-NEXT:    ldd r24, Y+1
-; CHECK-O0-NEXT:    ldd r25, Y+2
-; CHECK-O0-NEXT:    lsl r24
-; CHECK-O0-NEXT:    rol r25
-; CHECK-O0-NEXT:    subi r24, -lo8(arr0)
-; CHECK-O0-NEXT:    sbci r25, -hi8(arr0)
-; CHECK-O0-NEXT:    movw r30, r24
+; CHECK-O0-NEXT:    ldd r30, Y+1
+; CHECK-O0-NEXT:    ldd r31, Y+2
+; CHECK-O0-NEXT:    lsl r30
+; CHECK-O0-NEXT:    rol r31
+; CHECK-O0-NEXT:    subi r30, -lo8(arr0)
+; CHECK-O0-NEXT:    sbci r31, -hi8(arr0)
 ; CHECK-O0-NEXT:    lpm r24, Z+
 ; CHECK-O0-NEXT:    lpm r25, Z
 ; CHECK-O0-NEXT:    adiw r28, 2
@@ -95,11 +94,10 @@ define i8 @foo1(i16 %a) addrspace(1) {
 ; CHECK-O0-NEXT:    out 61, r28
 ; CHECK-O0-NEXT:    std Y+1, r24
 ; CHECK-O0-NEXT:    std Y+2, r25
-; CHECK-O0-NEXT:    ldd r24, Y+1
-; CHECK-O0-NEXT:    ldd r25, Y+2
-; CHECK-O0-NEXT:    subi r24, -lo8(arr1)
-; CHECK-O0-NEXT:    sbci r25, -hi8(arr1)
-; CHECK-O0-NEXT:    movw r30, r24
+; CHECK-O0-NEXT:    ldd r30, Y+1
+; CHECK-O0-NEXT:    ldd r31, Y+2
+; CHECK-O0-NEXT:    subi r30, -lo8(arr1)
+; CHECK-O0-NEXT:    sbci r31, -hi8(arr1)
 ; CHECK-O0-NEXT:    lpm r24, Z
 ; CHECK-O0-NEXT:    adiw r28, 2
 ; CHECK-O0-NEXT:    in r0, 63