[llvm] [GISel][RISCV]Implement indirect parameter passing (PR #95429)

[Gábor Spaits via llvm-commits]

================
@@ -16,6 +16,580 @@
 ; Check that on RV32, i64 is passed in a pair of registers. Unlike
 ; the convention for varargs, this need not be an aligned pair.
 
+define i64 @callee_128i_in_regs_stack_fst(i64 %x1, i64 %x2, i64 %x3, i64 %x4, i128 %y, i127 %y2) {
+  ; RV32I-LABEL: name: callee_128i_in_regs_stack_fst
+  ; RV32I: bb.1 (%ir-block.0):
+  ; RV32I-NEXT:   liveins: $x10, $x11, $x12, $x13, $x14, $x15, $x16, $x17
+  ; RV32I-NEXT: {{  $}}
+  ; RV32I-NEXT:   [[COPY:%[0-9]+]]:_(s32) = COPY $x10
+  ; RV32I-NEXT:   [[COPY1:%[0-9]+]]:_(s32) = COPY $x11
+  ; RV32I-NEXT:   [[MV:%[0-9]+]]:_(s64) = G_MERGE_VALUES [[COPY]](s32), [[COPY1]](s32)
+  ; RV32I-NEXT:   [[COPY2:%[0-9]+]]:_(s32) = COPY $x12
+  ; RV32I-NEXT:   [[COPY3:%[0-9]+]]:_(s32) = COPY $x13
+  ; RV32I-NEXT:   [[MV1:%[0-9]+]]:_(s64) = G_MERGE_VALUES [[COPY2]](s32), [[COPY3]](s32)
+  ; RV32I-NEXT:   [[COPY4:%[0-9]+]]:_(s32) = COPY $x14
+  ; RV32I-NEXT:   [[COPY5:%[0-9]+]]:_(s32) = COPY $x15
+  ; RV32I-NEXT:   [[MV2:%[0-9]+]]:_(s64) = G_MERGE_VALUES [[COPY4]](s32), [[COPY5]](s32)
+  ; RV32I-NEXT:   [[COPY6:%[0-9]+]]:_(s32) = COPY $x16
+  ; RV32I-NEXT:   [[COPY7:%[0-9]+]]:_(s32) = COPY $x17
+  ; RV32I-NEXT:   [[MV3:%[0-9]+]]:_(s64) = G_MERGE_VALUES [[COPY6]](s32), [[COPY7]](s32)
+  ; RV32I-NEXT:   [[FRAME_INDEX:%[0-9]+]]:_(p0) = G_FRAME_INDEX %fixed-stack.1
+  ; RV32I-NEXT:   [[LOAD:%[0-9]+]]:_(p0) = G_LOAD [[FRAME_INDEX]](p0) :: (load (s32) from %fixed-stack.1, align 16)
+  ; RV32I-NEXT:   [[LOAD1:%[0-9]+]]:_(s128) = G_LOAD [[LOAD]](p0) :: (load (s128) from stack, align 8)
+  ; RV32I-NEXT:   [[FRAME_INDEX1:%[0-9]+]]:_(p0) = G_FRAME_INDEX %fixed-stack.0
+  ; RV32I-NEXT:   [[LOAD2:%[0-9]+]]:_(p0) = G_LOAD [[FRAME_INDEX1]](p0) :: (load (s32) from %fixed-stack.0)
+  ; RV32I-NEXT:   [[LOAD3:%[0-9]+]]:_(s127) = G_LOAD [[LOAD2]](p0) :: (load (s127) from stack + 4, align 4, basealign 8)
----------------
spaits wrote:

Isn't this a replacement of G_PTR_ADD? In this case we want to load the second parameter from the stack, that is 4*8=32 bits away from the first parameter the first parameter.

I interpret this code like this.

https://github.com/llvm/llvm-project/pull/95429