[llvm] [bolt] Simplify rodata/literal load for X86_64 & AArch64 (PR #179474)

[Paschalis Mpeis via llvm-commits]

================
@@ -0,0 +1,76 @@
+// this test checks a load literal instructions changed to movk
+
+# REQUIRES: system-linux
+
+# RUN: %clang %cflags %s -Wa,--defsym,CIBIGFUNC=1 -Wl,-q -o %t.exe
+# RUN: llvm-bolt %t.exe -o %t.bolt --lite=0 \
+# RUN:    --keep-nops --eliminate-unreachable=false \
+# RUN:    | FileCheck %s --check-prefix=CHECK-LOGS
+
+# RUN: %clang %cflags %s -Wa,--defsym,CIOUTSIDEFUNC=1 -Wl,-q -o %t.exe
+# RUN: llvm-bolt %t.exe -o %t.bolt --lite=0 \
+# RUN:    --keep-nops --eliminate-unreachable=false \
+# RUN:    | FileCheck %s --check-prefix=CHECK-LOGS
+
+# CHECK-LOGS: simplified 2 out of 2 loads
+
+  .text
+  .align 4
+  .local foo
+  .type foo, %function
+foo:
+    stp x29, x30, [sp, #-32]!
+    stp x19, x20, [sp, #16]
+    mov x29, sp
+
+    mov w19, #0 // counter = 0
+    mov w22, #0 // result = 0
+
+    ldr w23, .Llimit
+    ldr x24, .LStep
+
+.ifdef CIBIGFUNC
+    b .LStub
+.LConstants:
+  .Llimit: .word 100
+  .LStep:  .xword 3
+.LStub:
+.rep 0x100000
+    nop
+.endr
+    b .Lmain_loop
+.endif
+
+.Lmain_loop:
+    madd w22, w19, w24, w22  // result += counter * increment
+    add w19, w19, #1
+    cmp w19, w23
+    b.lt .Lmain_loop
+    mov w0, w22
+    b .Lreturn_point
+.Lreturn_point:
+    ldp x19, x20, [sp, #16]
+    ldp x29, x30, [sp], #32
+    ret
+.size foo, .-foo
----------------
paschalis-mpeis wrote:

Could we do it via a `.space` directive?
BTW, do we still do the simplification even without going out of range?

https://github.com/llvm/llvm-project/pull/179474