[llvm] bafff3e - [RISCV][MC] Implicit 0-offset aliases for JR/JALR (#94688)

[via llvm-commits]

Author: Sam Elliott
Date: 2024-06-08T17:53:48+01:00
New Revision: bafff3e5316a33d6f016f6e9d6eb02020ad603b6

URL: https://github.com/llvm/llvm-project/commit/bafff3e5316a33d6f016f6e9d6eb02020ad603b6
DIFF: https://github.com/llvm/llvm-project/commit/bafff3e5316a33d6f016f6e9d6eb02020ad603b6.diff

LOG: [RISCV][MC] Implicit 0-offset aliases for JR/JALR (#94688)

This broadly follows how in almost all places, we accept `(<reg>)` to
mean `0(<reg>)`, but I think these are the first like this for Jumps
rather than Loads/Stores. These are accepted by binutils but not by
LLVM: https://godbolt.org/z/GK7MGE7q7

Added: 
    

Modified: 
    llvm/lib/Target/RISCV/RISCVInstrInfo.td
    llvm/test/MC/RISCV/rvi-aliases-valid.s

Removed: 
    


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diff  --git a/llvm/lib/Target/RISCV/RISCVInstrInfo.td b/llvm/lib/Target/RISCV/RISCVInstrInfo.td
index 010e07f65cec4..4cdf08a46f285 100644
--- a/llvm/lib/Target/RISCV/RISCVInstrInfo.td
+++ b/llvm/lib/Target/RISCV/RISCVInstrInfo.td
@@ -943,6 +943,9 @@ def : InstAlias<"ret",                   (JALR      X0,      X1, 0), 4>;
 def : InstAlias<"jr $rs, $offset",        (JALR      X0, GPR:$rs, simm12:$offset), 0>;
 def : InstAlias<"jalr $rs, $offset",      (JALR      X1, GPR:$rs, simm12:$offset), 0>;
 def : InstAlias<"jalr $rd, $rs, $offset", (JALR GPR:$rd, GPR:$rs, simm12:$offset), 0>;
+def : InstAlias<"jr (${rs})",             (JALR      X0, GPR:$rs, 0), 0>;
+def : InstAlias<"jalr (${rs})",           (JALR      X1, GPR:$rs, 0), 0>;
+def : InstAlias<"jalr $rd, (${rs})",      (JALR GPR:$rd, GPR:$rs, 0), 0>;
 
 def : InstAlias<"fence", (FENCE 0xF, 0xF)>; // 0xF == iorw
 

diff  --git a/llvm/test/MC/RISCV/rvi-aliases-valid.s b/llvm/test/MC/RISCV/rvi-aliases-valid.s
index 098d5c132c98c..9ac6a8a2c1e75 100644
--- a/llvm/test/MC/RISCV/rvi-aliases-valid.s
+++ b/llvm/test/MC/RISCV/rvi-aliases-valid.s
@@ -190,6 +190,16 @@ jalr x25, x26, 11
 # CHECK-S-OBJ-NOALIAS: jalr zero, 0(ra)
 # CHECK-S-OBJ: ret
 ret
+# CHECK-S-OBJ-NOALIAS: jalr zero, 0(s11)
+# CHECK-S-OBJ: jr s11
+jr (x27)
+# CHECK-S-OBJ-NOALIAS: jalr ra, 0(t3)
+# CHECK-S-OBJ: jalr t3
+jalr (x28)
+# CHECK-S-OBJ-NOALIAS: jalr t4, 0(t5)
+# CHECK-S-OBJ: jalr t4, t5
+jalr x29, (x30)
+
 # TODO call
 # TODO tail