[snippy] memory initialization support

Use the -init-memory= option to initialize memory.
Along with it, you must also provide the -init-regs-in-elf option.

Possible values of -init-memory= are:
 1. no - not initialize memory
 2. full - initialize all RW sections from the layout with random values
 3. full-with-addresses - add sections initialized with the addresses you
    specify here to the output .elf file
 4. runtile - use the initialization function. The RW sections will be marked as
    NOLOAD and the initialization function will be called in runtime to
    initialize the data section.
 5. loads – This setting is similar to runtime, but it only initializes the
    addresses that were accessed in the program.
 6. loads-with-addresses – This setting is similar to loads, but it only
    initializes legal addresses from the scheme.
 7. ascii-file – initialize memory as an ASCII file. Then, use it along with the
    --init-memory-file option to initialize memory in the format snippy uses to
    dump memory sections

Author: vberbenets-sc

llvm/test/tools/llvm-snippy/code-layout/code-layout-many-modules.yaml

@@ -0,0 +1,58 @@
+# RUN: llvm-snippy %s --model-plugin None -o %t
+# RUN: llvm-readelf -S %t.elf | FileCheck %s
+
+options:
+  mtriple: riscv64
+  enable-phdrs-definition: true
+  num-instrs: 100
+  init-memory: runtime
+  init-regs-in-elf: true
+
+sections:
+    - name:      1
+      VMA:       0x1000000
+      SIZE:      0x2000
+      LMA:       0x1000000
+      ACCESS:    rx
+      PHDR:      'header1'
+    - name:      2
+      VMA:       0x1002000
+      SIZE:      0x2000
+      LMA:       0x1002000
+      ACCESS:    rx
+      PHDR:      'header2'
+    - name:      3
+      VMA:       0x1000
+      SIZE:      0x1000
+      LMA:       0x1000
+      ACCESS:    rw
+      PHDR:      'header3'
+    - name:      4
+      VMA:       0x100000
+      SIZE:      0x1000
+      LMA:       0x100000
+      ACCESS:    r
+      PHDR:      'header3'
+
+code-layout:
+  ranges:
+    - start: 0x1000000
+      size: 0x2000
+      stride: 0x100
+      first-offset: 0
+      last-offset: 0xff
+    - start: 0x1002000
+      size: 0x2000
+      stride: 0x100
+      first-offset: 0
+      last-offset: 0xff
+histogram:
+    - [ADD, 3.0]
+    - [BLT, 1.0]
+    - [LD,  3.0]
+    - [SW,  3.0]
+
+# CHECK: .snippy.1.rx
+# CHECK-SAME: PROGBITS
+# CHECK: .snippy.2.rx
+# CHECK-SAME: PROGBITS

llvm/test/tools/llvm-snippy/code-layout/mem-init.yaml

@@ -0,0 +1,47 @@
+# RUN: llvm-snippy %s --model-plugin None -o %t
+# RUN: llvm-readelf -S %t.elf | FileCheck %s
+
+options:
+  mtriple: riscv64
+  num-instrs: 100
+  init-memory: runtime
+  init-regs-in-elf: true
+
+sections:
+    - name:      1
+      VMA:       0x100000
+      SIZE:      0x20000
+      LMA:       0x100000
+      ACCESS:    rx
+    - name:      2
+      VMA:       0x130000
+      SIZE:      0x20000
+      LMA:       0x130000
+      ACCESS:    rx
+    - name:      3
+      VMA:       0x200000
+      SIZE:      0x1000
+      LMA:       0x200000
+      ACCESS:    rw
+ 
+
+code-layout:
+  ranges:
+    - start: 0x100000
+      size: 0x10000
+      stride: 0x10000
+      first-offset: 0
+      last-offset: 0xffff
+    - start: 0x130000
+      size: 0x10000
+      stride: 0x10000
+      first-offset: 0
+      last-offset: 0xffff
+histogram:
+    - [ADD, 3.0]
+    - [BLT, 1.0]
+
+# CHECK: .snippy.1.rx
+# CHECK-SAME: PROGBITS
+# CHECK: .snippy.2.rx
+# CHECK-SAME: PROGBITS

llvm/test/tools/llvm-snippy/memory/file/Inputs/memory-map-additional-symbols.yaml

@@ -0,0 +1,7 @@
+Section {2}:
+0x0:  11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11
+
+end-of-sections-init
+
+Section {4}:
+0x0:  11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11

llvm/test/tools/llvm-snippy/memory/file/Inputs/memory-map-big.yaml

@@ -0,0 +1,5 @@
+Section {2}:
+0x0: Bf 00 11 6f 07
+0x5: bf 11 49 aa 55 77 91 02 01 10 
+0xf: 8F
+0x10: 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11

llvm/test/tools/llvm-snippy/memory/file/Inputs/memory-map-unaligned.yaml

@@ -0,0 +1,9 @@
+Section {2}:
+0x0: 11 
+0x1: 22
+0x2: 33
+0x3: 44
+0x4: 55
+0x5: 66
+0x6: 77
+0x7: 88

llvm/test/tools/llvm-snippy/memory/file/Inputs/memory-map-wrong-byte-format.yaml

@@ -0,0 +1,3 @@
+Section {2}:
+0x0:  11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11
+0x10: 11 11 11 11 11 BOBA 11 11 11 11 11 11 11 11 11 11

llvm/test/tools/llvm-snippy/memory/file/Inputs/memory-map-wrong-format.yaml

@@ -0,0 +1,2 @@
+Section {2}:
+0x0: 

llvm/test/tools/llvm-snippy/memory/file/Inputs/memory-map.yaml

@@ -0,0 +1,5 @@
+Section {2}:
+0x0:  11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11
+
+Section {4}:
+0x0:  11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11

llvm/test/tools/llvm-snippy/memory/file/ascii-default-run.yaml

@@ -0,0 +1,29 @@
+# RUN: llvm-snippy %s -model-plugin=None \
+# RUN:   --init-memory=ascii-file --init-memory-file=%S/Inputs/memory-map.yaml
+
+sections:
+  - name:      1
+    VMA:       0x100000
+    SIZE:      0x100000
+    LMA:       0x100000
+    ACCESS:    rx
+  - name:      2
+    VMA:       0x200000
+    SIZE:      0x000010
+    LMA:       0x200000
+    ACCESS:    rw
+  - name:      4
+    VMA:       0x400000
+    SIZE:      0x000010
+    LMA:       0x400000
+    ACCESS:    rw
+
+options:
+  mtriple: "riscv64"
+  mcpu: "generic-rv64"
+  num-instrs: 10
+  
+histogram:
+    - [LB, 2.0]
+    - [ADD, 4.0]
+    - [SW, 2.0]

llvm/test/tools/llvm-snippy/memory/file/negative-ascii-byte-parsing.yaml

@@ -0,0 +1,27 @@
+# RUN: not llvm-snippy %s -model-plugin=None \
+# RUN:   --init-memory-file=%S/Inputs/memory-map-wrong-byte-format.yaml \
+# RUN:   --init-memory=ascii-file |& FileCheck %s
+
+sections:
+  - name:      1
+    VMA:       0x210000
+    SIZE:      0x100000
+    LMA:       0x210000
+    ACCESS:    rx
+  - name:      2
+    VMA:       0x100000
+    SIZE:      0x001000
+    LMA:       0x100000
+    ACCESS:    rw
+
+options:
+  mtriple: "riscv64"
+  mcpu: "generic-rv64"
+  num-instrs: 10
+
+  
+histogram:
+    - [LB, 2.0]
+
+# CHECK: error: [memory-map-wrong-byte-format.yaml, 3] 
+# CHECK: Wrong memory init file format: can't convert to byte: BOBA