[EraVM][AsmPrinter] Emit initialization code for global variables.

This includes:

  1. Increasing the stack pointer according to the number of global variables.
    nop    stack+=[NumCells + r0]

  2. Duplication of intializers in the code section and copying them to
     corresponding stack items.
    add    @glob_initializer[0], r0, stack[@glob]
    ...

  3. Generation of default landing pads.
    DEFAULT_UNWIND:
        ret.panic.to_label @DEFAULT_UNWIND
    DEFAULT_FAR_RETURN:
        ret.ok.to_label r1,    @DEFAULT_FAR_RETURN
    DEFAULT_FAR_REVERT:
        ret.revert.to_label r1,    @DEFAULT_FAR_REVERT

Author: PavelKopyl

lld/test/ELF/Inputs/eravm-binary-layout-hash.lds

@@ -0,0 +1,43 @@
+ENTRY(0)
+SECTIONS {
+  .code : SUBALIGN(8) {
+    *(.text)
+
+    ASSERT((32 - (31 & .)) % 8 == 0, "padding isn't multiple of 8");
+    /* Check the code size is no more than 2^16 instructions. */
+    ASSERT(. <= (1 << 16) * 8, "number of instructions > 2^16");
+    /* Align the .rodata to 32 bytes. */
+    . = (. + 31) & ~31;
+    *(.rodata)
+
+    ASSERT(. % 32 == 0, "size isn't multiple of 32");
+
+    /* Add padding with metadata */
+    . = ((((. + 32) >> 5) | 1 ) << 5) - 13;
+
+    BYTE(0x3A);
+    BYTE(0xC2);
+    BYTE(0x25);
+    BYTE(0x16);
+    BYTE(0x8D);
+    BYTE(0xF5);
+    BYTE(0x42);
+    BYTE(0x12);
+    BYTE(0xA2);
+    BYTE(0x5C);
+    BYTE(0x1C);
+    BYTE(0x01);
+    BYTE(0xFD);
+
+    ASSERT(. % 64 == 32, "size isn't odd number of words");
+
+    /* Check the total binary size is no more than (2^16 - 2) words. */
+    ASSERT(. <= ((1 << 16) - 1) * 32, "Binary size > (2^16 - 2) words")
+  } = 0
+
+  /* .data section itself that contains initializers of global variables,
+   is not needed. */
+  /DISCARD/ : {
+    *(.data)
+  }
+}

lld/test/ELF/Inputs/eravm-binary-layout.lds

@@ -0,0 +1,25 @@
+ENTRY(0)
+SECTIONS {
+  .code : SUBALIGN(8) {
+    *(.text)
+
+    ASSERT((32 - (31 & .)) % 8 == 0, "padding isn't multiple of 8");
+
+    /* Align the .rodata to 32 bytes. */
+    . = (. + 31) & ~31;
+    *(.rodata)
+
+    ASSERT(. % 32 == 0, "size isn't multiple of 32");
+
+    /* Add padding such that the size be odd number of words */
+    . = ((. >> 5) | 1) << 5;
+
+    ASSERT(. % 64 == 32, "size isn't odd number of words");
+  } = 0
+
+  /* .data section itself that contains initializers of global variables,
+     is not needed. */
+  /DISCARD/ : {
+    *(.data)
+  }
+}

lld/test/ELF/Inputs/eravm.lds

@@ -1,4 +1,5 @@
 /* Not a real EraVM memory layout. */
+ENTRY(0)
 MEMORY {
   code (rx)   : ORIGIN = 0,  LENGTH = 4K
   stack (w!x) : ORIGIN = 4K, LENGTH = 4K

lld/test/ELF/eravm-binary-layout.s

@@ -0,0 +1,86 @@
+; REQUIRES: eravm
+; RUN: llvm-mc -filetype=obj -arch=eravm %s -o %t.o
+; RUN: ld.lld -T %S/Inputs/eravm-binary-layout.lds %t.o -o %t
+; RUN: llvm-objdump --no-leading-addr  --disassemble-all --disassemble-zeroes --reloc --syms %t   | FileCheck --check-prefix=OUTPUT %s
+; RUN: ld.lld -T %S/Inputs/eravm-binary-layout-hash.lds %t.o -o %t
+; RUN: llvm-objdump --no-leading-addr  --disassemble-all --disassemble-zeroes --reloc --syms %t   | FileCheck --check-prefix=OUTPUT-HASH %s
+
+        .text
+	nop	stack+=[2 + r0]
+	add	@glob_initializer[0], r0, stack[@glob]
+
+	.globl	get_glob
+get_glob:
+	add	3, r0, r1
+	add	stack[@glob], r1, r1
+	ret
+
+DEFAULT_UNWIND:
+	ret.panic.to_label @DEFAULT_UNWIND
+DEFAULT_FAR_RETURN:
+	ret.ok.to_label	r1, @DEFAULT_FAR_RETURN
+DEFAULT_FAR_REVERT:
+	ret.revert.to_label r1, @DEFAULT_FAR_REVERT
+
+	.data
+	.globl	glob                            ; @glob
+	.p2align	5, 0x0
+glob:
+	.cell	113
+
+	.globl	glob_ptr                    ; @glob_ptr
+	.p2align	5, 0x0
+glob_ptr:
+	.cell	0
+
+	.rodata
+glob_initializer:
+	.cell	113
+
+; OUTPUT:      SYMBOL TABLE:
+; OUTPUT-NEXT: 00000040 l       .code	00000000 glob_initializer
+; OUTPUT-NEXT: 00000028 l       .code	00000000 DEFAULT_UNWIND
+; OUTPUT-NEXT: 00000030 l       .code	00000000 DEFAULT_FAR_RETURN
+; OUTPUT-NEXT: 00000038 l       .code	00000000 DEFAULT_FAR_REVERT
+; OUTPUT-NEXT: 00000010 g       .code	00000000 get_glob
+; OUTPUT-EMPTY:
+; OUTPUT-LABEL: <.code>:
+; OUTPUT-NEXT: 00 02 00 00 00 00 00 02       	nop	stack+=[2 + r0]
+; OUTPUT-NEXT: 00 00 00 02 00 00 00 47       	add	code[2], r0, stack[r0]
+; OUTPUT-EMPTY:
+; OUTPUT-NEXT: <get_glob>:
+; OUTPUT-NEXT: 00 00 00 03 01 00 00 39       	add	3, r0, r1
+; OUTPUT-NEXT: 00 00 00 00 01 10 00 31       	add	stack[r0], r1, r1
+; OUTPUT-NEXT: 00 00 00 00 00 01 04 2d       	ret
+; OUTPUT-EMPTY:
+; OUTPUT-NEXT: <DEFAULT_UNWIND>:
+; OUTPUT-NEXT: 00 00 00 05 00 00 04 32       	ret.panic.to_label  5
+; OUTPUT-EMPTY:
+; OUTPUT-NEXT: <DEFAULT_FAR_RETURN>:
+; OUTPUT-NEXT: 00 00 00 06 00 01 04 2e       	ret.ok.to_label	r1, 6
+; OUTPUT-EMPTY:
+; OUTPUT-NEXT: <DEFAULT_FAR_REVERT>:
+; OUTPUT-NEXT: 00 00 00 07 00 01 04 30       	ret.revert.to_label	r1, 7
+; OUTPUT-EMPTY:
+; OUTPUT-NEXT: <glob_initializer>:
+; OUTPUT-NEXT: 00 00 00 00 00 00 00 00
+; OUTPUT-NEXT: 00 00 00 00 00 00 00 00
+; OUTPUT-NEXT: 00 00 00 00 00 00 00 00
+; OUTPUT-NEXT: 00 00 00 00 00 00 00 71
+
+; OUTPUT-HASH: <glob_initializer>:
+; OUTPUT-HASH-NEXT: 00 00 00 00 00 00 00 00
+; OUTPUT-HASH-NEXT: 00 00 00 00 00 00 00 00
+; OUTPUT-HASH-NEXT: 00 00 00 00 00 00 00 00
+; OUTPUT-HASH-NEXT: 00 00 00 00 00 00 00 71
+; Next zeroed bytes are added to make the total .code size
+; the even number of words (32 bytes each).
+; OUTPUT-HASH-NEXT: 00 00 00 00 00 00 00 00
+; OUTPUT-HASH-NEXT: 00 00 00 00 00 00 00 00
+; OUTPUT-HASH-NEXT: 00 00 00 00 00 00 00 00
+; OUTPUT-HASH-NEXT: 00 00 00 00 00 00 00 00
+; OUTPUT-HASH-NEXT: 00 00 00 00 00 00 00 00
+; OUTPUT-HASH-NEXT: 00 00 00 00 00 00 00 00
+; OUTPUT-HASH-NEXT: 00 00 00 3a c2 25 16 8d
+; OUTPUT-HASH-NEXT: f5 42 12 a2 5c 1c 01 fd
+; The last 13 bytes are the hash value.