Skip to content

[RISCV] Remove outdated c.lui rd, 0 to c.li rd, 0 rewriting. NFCI #1268

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Closed
Jonathon Penix (jonathonpenix) wants to merge 2 commits into from
Closed

[RISCV] Remove outdated c.lui rd, 0 to c.li rd, 0 rewriting. NFCI #1268

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
762c841
[RISCV] Remove outdated `c.lui rd, 0` to `c.li rd, 0` rewriting. NFCI
jonathonpenix Jun 8, 2026
abb9d7a
Add explicit checks that c.lui can't be generated
jonathonpenix Jun 26, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
2 changes: 0 additions & 2 deletions lib/Target/RISCV/RISCVHelper.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -276,8 +276,6 @@ template <typename T> T encodeCJ(T Result) {
}

template <typename T> T encodeCI(T Result) {
// `c.lui rd, 0` is illegal, it will be converted to `c.li rd, 0` when
// applying
uint16_t Imm17 = extractBits(Result, 17, 17) << 12;
uint16_t Imm16_12 = extractBits(Result, 16, 12) << 2;
Result = Imm17 | Imm16_12;
Expand Down
13 changes: 3 additions & 10 deletions lib/Target/RISCV/RISCVRelocationCompute.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -102,8 +102,8 @@ uint64_t clearImmediateBits(uint64_t Instr, EncodingType Type) {
return Instr & 0x00000000C00FFFFFull;
case EncTy_QC_ES:
return Instr & 0x00000000C1FFF07Full;
/* C.LUI/C.LI clearing handled in doRelocHelper */
case EncTy_CI:
return Instr & 0xEF83;
/* No overwriting being performed */
case EncTy_None:
case EncTy_LEB128:
Expand Down Expand Up @@ -142,16 +142,9 @@ uint64_t doRelocHelper(const RelocationInfo &RelocInfo, uint64_t Instruction,
case EncTy_CJ:
Value = encodeCJ(Value);
break;
case EncTy_CI: {
if (Value >> 12 == 0) {
// `c.lui rd, 0` is illegal, convert to `c.li rd, 0`
return (Instruction & 0x0F83) | 0x4000;
} else {
Instruction &= 0xEF83;
Value = encodeCI(Value);
}
case EncTy_CI:
Value = encodeCI(Value);
break;
}
case EncTy_QC_EB:
Value = encodeQCEB(Value);
break;
Expand Down
16 changes: 16 additions & 0 deletions test/RISCV/standalone/Relaxation/HI20_LO12_I_TO_CLUI/HI20_LO12_I_TO_CLUI.test
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -170,6 +170,22 @@ CHECK-NEXT: 80402503 lw a0, -2044(zero)
CHECK-NEXT: 00001137 lui sp, 1
CHECK-NEXT: 80412503 lw a0, -2044(sp)

## Check that --no-relax-zero is honored. Also check that a c.lui with imm 0
## is not generated.
RUN: %clang %clangopts -c %p/Inputs/1.s -o %t.1.o
RUN: %link %linkopts -MapStyle txt -Map %t.1.map --verbose --no-relax-zero %t.1.o -o %t.1.no-relax-zero.out -T %p/Inputs/1.t 2>&1 | %filecheck %s --check-prefix=VERBOSE-NO-RELAX-ZERO
VERBOSE-NO-RELAX-ZERO-NOT: RISCV_LUI_ZERO : Deleting [[#]] bytes
VERBOSE-NO-RELAX-ZERO-NOT: RISCV_LUI_C : Deleting 2 bytes for symbol 'B'
VERBOSE-NO-RELAX-ZERO-NOT: RISCV_LUI_C : relaxing instruction {{.*}} for symbol B
VERBOSE-NO-RELAX-ZERO-NOT: RISCV_LUI_C : Deleting 2 bytes for symbol 'C'
VERBOSE-NO-RELAX-ZERO-NOT: RISCV_LUI_C : relaxing instruction {{.*}} for symbol C

RUN: %objdump --no-print-imm-hex -d %t.1.no-relax-zero.out 2>&1 | %filecheck %s --check-prefix=NO-RELAX-ZERO-DUMP

NO-RELAX-ZERO-DUMP: <.text>:
NO-RELAX-ZERO-DUMP-NEXT: 00000537 lui a0, 0
NO-RELAX-ZERO-DUMP-NEXT: 00052503 lw a0, 0(a0)
NO-RELAX-ZERO-DUMP-NEXT: 00000537 lui a0, 0
NO-RELAX-ZERO-DUMP-NEXT: 7fc52503 lw a0, 2044(a0)
NO-RELAX-ZERO-DUMP-NEXT: 00000537 lui a0, 0
NO-RELAX-ZERO-DUMP-NEXT: 80452503 lw a0, -2044(a0)
Loading