[RISCV] replace unuseful emergency spill slot test with a mir test

[StephenFan]

Summary

It seems that the original emergency spill slot test doesn't use the emergency spill slot. So I replaced it with a mir test

[StephenFan]

Ping.

[luismarques]

From some quick testing, it seemed that you could trim this test down a bit.
You're also adding # REQUIRES: asserts but not actually checking for any debug output.
Also, it would be nice to add a comment documenting the logic of this test, unless new CHECKs of the debug output make it more obvious.

[StephenFan]

Address @luismarques 's comment

[rogfer01]

Isn't this very similar to https://github.com/llvm/llvm-project/blob/main/llvm/test/CodeGen/RISCV/out-of-reach-emergency-slot.mir except for a missing SD?

[StephenFan]

In D97274#2593601, @rogfer01 wrote:

Isn't this very similar to https://github.com/llvm/llvm-project/blob/main/llvm/test/CodeGen/RISCV/out-of-reach-emergency-slot.mir except for a missing SD?

Yes, I referenced this out-of-reach-emergency-slot.mir test. But with a stack object that has a out-of-range size. And I think my use-emergency-spill-slot.mir test and out-of-reach-emergency-slot.mir test are a little repeated. So should I keep my use-emergency-spill-slot.mir test or delete it?

[rogfer01]

Yes, I referenced this out-of-reach-emergency-slot.mir test. But with a stack object that has a out-of-range size. And I think my use-emergency-spill-slot.mir test and out-of-reach-emergency-slot.mir test are a little repeated. So should I keep my use-emergency-spill-slot.mir test or delete it?

Oh sorry I failed to notice you also adjusted maxAlignment to something sensible. Both look very similar but we could argue they are testing different things, so I think this can be useful.

llvm/test/CodeGen/RISCV/large-stack.ll

 ; RV32I-WITHFP-NEXT:    addi a0, a0, -352
 ; RV32I-WITHFP-NEXT:    add sp, sp, a0
 ; RV32I-WITHFP-NEXT:    lw s0, 2024(sp) # 4-byte Folded Reload
 ; RV32I-WITHFP-NEXT:    lw ra, 2028(sp) # 4-byte Folded Reload
 ; RV32I-WITHFP-NEXT:    addi sp, sp, 2032
 ; RV32I-WITHFP-NEXT:    ret
   %tmp = alloca [ 305419896 x i8 ] , align 4
   ret void
-}
-
-; This test case artificially produces register pressure which should force
-; use of the emergency spill slot.
-
-define void @test_emergency_spill_slot(i32 %a) {
-; RV32I-FPELIM-LABEL: test_emergency_spill_slot:
-; RV32I-FPELIM:       # %bb.0:
-; RV32I-FPELIM-NEXT:    addi sp, sp, -2032
-; RV32I-FPELIM-NEXT:    .cfi_def_cfa_offset 2032
-; RV32I-FPELIM-NEXT:    sw s0, 2028(sp) # 4-byte Folded Spill
-; RV32I-FPELIM-NEXT:    sw s1, 2024(sp) # 4-byte Folded Spill
-; RV32I-FPELIM-NEXT:    .cfi_offset s0, -4
-; RV32I-FPELIM-NEXT:    .cfi_offset s1, -8
-; RV32I-FPELIM-NEXT:    lui a1, 97
-; RV32I-FPELIM-NEXT:    addi a1, a1, 672
-; RV32I-FPELIM-NEXT:    sub sp, sp, a1
-; RV32I-FPELIM-NEXT:    .cfi_def_cfa_offset 400016
-; RV32I-FPELIM-NEXT:    lui a1, 78
-; RV32I-FPELIM-NEXT:    addi a1, a1, 512
-; RV32I-FPELIM-NEXT:    addi a2, sp, 8
-; RV32I-FPELIM-NEXT:    add a1, a2, a1
-; RV32I-FPELIM-NEXT:    #APP
-; RV32I-FPELIM-NEXT:    nop
-; RV32I-FPELIM-EMPTY:
-; RV32I-FPELIM-NEXT:    #NO_APP
-; RV32I-FPELIM-NEXT:    sw a0, 0(a1)
-; RV32I-FPELIM-NEXT:    #APP
-; RV32I-FPELIM-NEXT:    nop
-; RV32I-FPELIM-EMPTY:
-; RV32I-FPELIM-NEXT:    #NO_APP
-; RV32I-FPELIM-NEXT:    lui a0, 97
-; RV32I-FPELIM-NEXT:    addi a0, a0, 672
-; RV32I-FPELIM-NEXT:    add sp, sp, a0
-; RV32I-FPELIM-NEXT:    lw s1, 2024(sp) # 4-byte Folded Reload
-; RV32I-FPELIM-NEXT:    lw s0, 2028(sp) # 4-byte Folded Reload
-; RV32I-FPELIM-NEXT:    addi sp, sp, 2032
-; RV32I-FPELIM-NEXT:    ret
-;
-; RV32I-WITHFP-LABEL: test_emergency_spill_slot:
-; RV32I-WITHFP:       # %bb.0:
-; RV32I-WITHFP-NEXT:    addi sp, sp, -2032
-; RV32I-WITHFP-NEXT:    .cfi_def_cfa_offset 2032
-; RV32I-WITHFP-NEXT:    sw ra, 2028(sp) # 4-byte Folded Spill
-; RV32I-WITHFP-NEXT:    sw s0, 2024(sp) # 4-byte Folded Spill
-; RV32I-WITHFP-NEXT:    sw s1, 2020(sp) # 4-byte Folded Spill
-; RV32I-WITHFP-NEXT:    sw s2, 2016(sp) # 4-byte Folded Spill
-; RV32I-WITHFP-NEXT:    .cfi_offset ra, -4
-; RV32I-WITHFP-NEXT:    .cfi_offset s0, -8
-; RV32I-WITHFP-NEXT:    .cfi_offset s1, -12
-; RV32I-WITHFP-NEXT:    .cfi_offset s2, -16
-; RV32I-WITHFP-NEXT:    addi s0, sp, 2032
-; RV32I-WITHFP-NEXT:    .cfi_def_cfa s0, 0
-; RV32I-WITHFP-NEXT:    lui a1, 97
-; RV32I-WITHFP-NEXT:    addi a1, a1, 688
-; RV32I-WITHFP-NEXT:    sub sp, sp, a1
-; RV32I-WITHFP-NEXT:    lui a1, 78
-; RV32I-WITHFP-NEXT:    addi a1, a1, 512
-; RV32I-WITHFP-NEXT:    lui a2, 1048478
-; RV32I-WITHFP-NEXT:    addi a2, a2, 1388
-; RV32I-WITHFP-NEXT:    add a2, s0, a2
-; RV32I-WITHFP-NEXT:    mv a2, a2
-; RV32I-WITHFP-NEXT:    add a1, a2, a1
-; RV32I-WITHFP-NEXT:    #APP
-; RV32I-WITHFP-NEXT:    nop
-; RV32I-WITHFP-EMPTY:
-; RV32I-WITHFP-NEXT:    #NO_APP
-; RV32I-WITHFP-NEXT:    sw a0, 0(a1)
-; RV32I-WITHFP-NEXT:    #APP
-; RV32I-WITHFP-NEXT:    nop
-; RV32I-WITHFP-EMPTY:
-; RV32I-WITHFP-NEXT:    #NO_APP
-; RV32I-WITHFP-NEXT:    lui a0, 97
-; RV32I-WITHFP-NEXT:    addi a0, a0, 688
-; RV32I-WITHFP-NEXT:    add sp, sp, a0
-; RV32I-WITHFP-NEXT:    lw s2, 2016(sp) # 4-byte Folded Reload
-; RV32I-WITHFP-NEXT:    lw s1, 2020(sp) # 4-byte Folded Reload
-; RV32I-WITHFP-NEXT:    lw s0, 2024(sp) # 4-byte Folded Reload
-; RV32I-WITHFP-NEXT:    lw ra, 2028(sp) # 4-byte Folded Reload
-; RV32I-WITHFP-NEXT:    addi sp, sp, 2032
-; RV32I-WITHFP-NEXT:    ret
-  %data = alloca [ 100000 x i32 ] , align 4
-  %ptr = getelementptr inbounds [100000 x i32], [100000 x i32]* %data, i32 0, i32 80000
-  %1 = tail call { i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32 } asm sideeffect "nop", "=r,=r,=r,=r,=r,=r,=r,=r,=r,=r,=r,=r,=r,=r,=r"()
-  %asmresult0 = extractvalue { i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32 } %1, 0
-  %asmresult1 = extractvalue { i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32 } %1, 1
-  %asmresult2 = extractvalue { i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32 } %1, 2
-  %asmresult3 = extractvalue { i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32 } %1, 3
-  %asmresult4 = extractvalue { i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32 } %1, 4
-  %asmresult5 = extractvalue { i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32 } %1, 5
-  %asmresult6 = extractvalue { i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32 } %1, 6
-  %asmresult7 = extractvalue { i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32 } %1, 7
-  %asmresult8 = extractvalue { i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32 } %1, 8
-  %asmresult9 = extractvalue { i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32 } %1, 9
-  %asmresult10 = extractvalue { i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32 } %1, 10
-  %asmresult11 = extractvalue { i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32 } %1, 11
-  %asmresult12 = extractvalue { i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32 } %1, 12
-  %asmresult13 = extractvalue { i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32 } %1, 13
-  %asmresult14 = extractvalue { i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32 } %1, 14
-  store volatile i32 %a, i32* %ptr
-  tail call void asm sideeffect "nop", "r,r,r,r,r,r,r,r,r,r,r,r,r,r,r"(i32 %asmresult0, i32 %asmresult1, i32 %asmresult2, i32 %asmresult3, i32 %asmresult4, i32 %asmresult5, i32 %asmresult6, i32 %asmresult7, i32 %asmresult8, i32 %asmresult9, i32 %asmresult10, i32 %asmresult11, i32 %asmresult12, i32 %asmresult13, i32 %asmresult14)
-  ret void
-}
+}

llvm/test/CodeGen/RISCV/use-emergency-spill-slot.mir

+# NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+# REQUIRES: asserts
+# RUN: llc -mtriple riscv64 -start-before=prologepilog -o - \
+# RUN:     -verify-machineinstrs %s | FileCheck %s
+#
+# RUN: llc -mtriple riscv64 -debug -run-pass=prologepilog -o /dev/null \
+# RUN:     -verify-machineinstrs %s 2>&1 \
+# RUN:     | FileCheck --check-prefix=DEBUG %s
+#
+# DEBUG: Scavenged register with spill: $x10 until %1:gpr = frame-setup LUI 1
+--- |
+  ; ModuleID = 'reduced.ll'
+  source_filename = "frame_layout-1253b1.cpp"
+  target datalayout = "e-m:e-p:64:64-i64:64-i128:128-n64-S128"
+  target triple = "riscv64"
+
+  ; Function Attrs: nounwind
+  define weak_odr dso_local void @foo(i8* %ay) nounwind {
+  ; CHECK-LABEL: foo:
+  ; CHECK:       # %bb.0: # %entry
+  ; CHECK-NEXT:    addi sp, sp, -2032
+  ; CHECK-NEXT:    sd ra, 2024(sp)                    # 8-byte Folded Spill
+  ; CHECK-NEXT:    sd a0, 0(sp)
+  ; CHECK-NEXT:    lui  a0, 1
+  ; CHECK-NEXT:    addiw  a0, a0, -2000
+  ; CHECK-NEXT:    sub  sp, sp, a0
+  ; CHECK-NEXT:    ld a0, 0(sp)
+  ; CHECK-NEXT:    call foo@plt
+  ; CHECK-NEXT:    lui  a0, 1
+  ; CHECK-NEXT:    addiw  a0, a0, -2000
+  ; CHECK-NEXT:    add  sp, sp, a0
+  ; CHECK-NEXT:    ld ra, 2024(sp)                    # 8-byte Folded Reload
+  ; CHECK-NEXT:    addi sp, sp, 2032
+  ; CHECK-NEXT:    ret
+  entry:
+    ret void
+  }
+
+
+...
+---
+name:            foo
+alignment:       2
+tracksRegLiveness: false
+frameInfo:
+  maxAlignment:    16
+stack:
+  - { id: 0, size: 8, alignment: 8 }
+  - { id: 1, size: 4096, alignment: 8 }
+machineFunctionInfo: {}
+body:             |
+  bb.0.entry:
+    liveins: $x1, $x5, $x6, $x7, $x10, $x11, $x12, $x13, $x14, $x15, $x16, $x17, $x28, $x29, $x30, $x31
+
+    ; At this point, all of the non-callee saved registers are liveins. 
+    ; Because of the stack size is out-of-range of a 12 bits immediate,
+    ; PEI will create a virtual register as temp register to make up a immediate 
+    ; that is out-of-range, which need to be Scavenged by RegScavenger.
+    ; However, at this point, all of the non-callee saved registers are liveins,
+    ; So use a emergency spill slot to free a register to replace the virtual register 
+    ; created before.
+    PseudoCALL target-flags(riscv-plt) @foo, csr_ilp32_lp64, implicit-def $x1, implicit-def $x2, implicit $x1, implicit $x5, implicit $x6, implicit $x7, implicit $x10, implicit $x11, implicit $x12, implicit $x13, implicit $x14, implicit $x15, implicit $x16, implicit $x17, implicit $x28, implicit $x29, implicit $x30, implicit $x31
+    PseudoRET
+
+...