[llvm] af6c43c - [LoongArch] Allow %pc_lo12 relocs in JIRL's immediate operand position

[Weining Lu via llvm-commits]

Author: WANG Xuerui
Date: 2023-01-22T18:49:29+08:00
New Revision: af6c43c8e99b0263d8050d2a85a0fbc5bc8b45ed

URL: https://github.com/llvm/llvm-project/commit/af6c43c8e99b0263d8050d2a85a0fbc5bc8b45ed
DIFF: https://github.com/llvm/llvm-project/commit/af6c43c8e99b0263d8050d2a85a0fbc5bc8b45ed.diff

LOG: [LoongArch] Allow %pc_lo12 relocs in JIRL's immediate operand position

Currently, gcc-13 will generate such assembly when `-mcmodel=medium`,
which is ostensibly a dirty hack to allow bigger offsets for extern
function calls without having to add more reloc types. This is not the
best way to accomplish the original goal, but such usages will appear
soon and we have to support it anyway.

Example:

```c
extern int foo(int);

int bar(int x) {
    return foo(x + 123);
}
```

will produce the following (simplified) assembly when compiled with
`-O2 -mcmodel=medium`:

```
    .globl  bar
    .type   bar, @function
bar:
    .cfi_startproc
    addi.w  $r4,$r4,123
    pcalau12i   $r12,%pc_hi20(foo)
    jirl    $r0,$r12,%pc_lo12(foo)
    .cfi_endproc
```

Reviewed By: SixWeining, wangleiat, MaskRay, xry111

Differential Revision: https://reviews.llvm.org/D142278

Added: 
    

Modified: 
    llvm/lib/Target/LoongArch/AsmParser/LoongArchAsmParser.cpp
    llvm/test/MC/LoongArch/Relocations/relocations.s

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Target/LoongArch/AsmParser/LoongArchAsmParser.cpp b/llvm/lib/Target/LoongArch/AsmParser/LoongArchAsmParser.cpp
index 4406808bcc188..9d6d981bb9082 100644
--- a/llvm/lib/Target/LoongArch/AsmParser/LoongArchAsmParser.cpp
+++ b/llvm/lib/Target/LoongArch/AsmParser/LoongArchAsmParser.cpp
@@ -318,7 +318,8 @@ class LoongArchOperand : public MCParsedAsmOperand {
     LoongArchMCExpr::VariantKind VK = LoongArchMCExpr::VK_LoongArch_None;
     bool IsConstantImm = evaluateConstantImm(getImm(), Imm, VK);
     bool IsValidKind = VK == LoongArchMCExpr::VK_LoongArch_None ||
-                       VK == LoongArchMCExpr::VK_LoongArch_B16;
+                       VK == LoongArchMCExpr::VK_LoongArch_B16 ||
+                       VK == LoongArchMCExpr::VK_LoongArch_PCALA_LO12;
     return IsConstantImm
                ? isShiftedInt<16, 2>(Imm) && IsValidKind
                : LoongArchAsmParser::classifySymbolRef(getImm(), VK) &&

diff  --git a/llvm/test/MC/LoongArch/Relocations/relocations.s b/llvm/test/MC/LoongArch/Relocations/relocations.s
index 5044b459dd95d..042cc93470a1e 100644
--- a/llvm/test/MC/LoongArch/Relocations/relocations.s
+++ b/llvm/test/MC/LoongArch/Relocations/relocations.s
@@ -74,6 +74,11 @@ addi.d $t1, $t1, %pc_lo12(foo+4)
 # INSTR: addi.d  $t1, $t1, %pc_lo12(foo+4)
 # FIXUP: fixup A - offset: 0, value: %pc_lo12(foo+4), kind: FK_NONE
 
+jirl $zero, $t1, %pc_lo12(foo)
+# RELOC: R_LARCH_PCALA_LO12 foo 0x0
+# INSTR: jirl $zero, $t1, %pc_lo12(foo)
+# FIXUP: fixup A - offset: 0, value: %pc_lo12(foo), kind: FK_NONE
+
 st.b $t1, $a2, %pc_lo12(foo)
 # RELOC: R_LARCH_PCALA_LO12 foo 0x0
 # INSTR: st.b  $t1, $a2, %pc_lo12(foo)