[llvm] 1582bcd - RISCV: handle 64-bit PCREL data relocations
Saleem Abdulrasool via llvm-commits
llvm-commits at lists.llvm.org
Tue Jun 14 14:39:47 PDT 2022
Author: Saleem Abdulrasool
Date: 2022-06-14T21:39:16Z
New Revision: 1582bcd0038dbf0b82f11f105ded0b223a40fcec
URL: https://github.com/llvm/llvm-project/commit/1582bcd0038dbf0b82f11f105ded0b223a40fcec
DIFF: https://github.com/llvm/llvm-project/commit/1582bcd0038dbf0b82f11f105ded0b223a40fcec.diff
LOG: RISCV: handle 64-bit PCREL data relocations
We would previously fail to handle 64-bit PC-relative relocations on
RISCV. This was exposed by trying to build with
`-fprofile-instr-generate`.
The original changes restricted the relocation handling to the text
segment as the paired relocations are undesirable in at least the debug
and .eh_frame sections. We now make this explicit to handle the general
case for the data relocations as well.
It would be preferable to use `R_RISCV_n_PCREL` when available to avoid
an extra relocation.
Differential Revision: https://reviews.llvm.org/D127549
Reviewed By: luismarques, MaskRay
Fixes: #55971
Added:
llvm/test/MC/RISCV/riscv64-64b-pcrel.s
Modified:
llvm/lib/Target/RISCV/MCTargetDesc/RISCVELFStreamer.cpp
Removed:
################################################################################
diff --git a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVELFStreamer.cpp b/llvm/lib/Target/RISCV/MCTargetDesc/RISCVELFStreamer.cpp
index 7d478a21913cd..294e69f89fe6f 100644
--- a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVELFStreamer.cpp
+++ b/llvm/lib/Target/RISCV/MCTargetDesc/RISCVELFStreamer.cpp
@@ -207,6 +207,10 @@ class RISCVELFStreamer : public MCELFStreamer {
static bool requiresFixups(MCContext &C, const MCExpr *Value,
const MCExpr *&LHS, const MCExpr *&RHS) {
+ auto IsMetadataOrEHFrameSection = [](const MCSection &S) -> bool {
+ return S.getKind().isMetadata() || S.getName() == ".eh_frame";
+ };
+
const auto *MBE = dyn_cast<MCBinaryExpr>(Value);
if (MBE == nullptr)
return false;
@@ -225,10 +229,15 @@ class RISCVELFStreamer : public MCELFStreamer {
MCConstantExpr::create(E.getConstant(), C), C);
RHS = E.getSymB();
- return (A.isInSection() ? A.getSection().hasInstructions()
- : !A.getName().empty()) ||
- (B.isInSection() ? B.getSection().hasInstructions()
- : !B.getName().empty());
+ // TODO: when available, R_RISCV_n_PCREL should be preferred.
+
+ // Avoid pairwise relocations for symbolic
diff erence in debug and .eh_frame
+ if (A.isInSection())
+ return !IsMetadataOrEHFrameSection(A.getSection());
+ if (B.isInSection())
+ return !IsMetadataOrEHFrameSection(B.getSection());
+ // as well as for absolute symbols.
+ return !A.getName().empty() || !B.getName().empty();
}
void reset() override {
diff --git a/llvm/test/MC/RISCV/riscv64-64b-pcrel.s b/llvm/test/MC/RISCV/riscv64-64b-pcrel.s
new file mode 100644
index 0000000000000..f2b84b17ede7f
--- /dev/null
+++ b/llvm/test/MC/RISCV/riscv64-64b-pcrel.s
@@ -0,0 +1,37 @@
+# RUN: llvm-mc -triple riscv64-unknown-linux-gnu -filetype obj -o - %s \
+# RUN: | llvm-readobj -r - | FileCheck %s
+
+# CHECK: Relocations [
+# CHECK: .relasx {
+# CHECK-NEXT: 0x0 R_RISCV_ADD64 y 0x0
+# CHECK-NEXT: 0x0 R_RISCV_SUB64 x 0x0
+# CHECK: }
+# CHECK: .relasy {
+# CHECK-NEXT: 0x0 R_RISCV_ADD64 x 0x0
+# CHECK-NEXT: 0x0 R_RISCV_SUB64 y 0x0
+# CHECK: }
+# CHECK: .relasz {
+# CHECK-NEXT: 0x0 R_RISCV_ADD64 z 0x0
+# CHECK-NEXT: 0x0 R_RISCV_SUB64 a 0x0
+# CHECK: }
+# CHECK: .relasa {
+# CHECK-NEXT: 0x0 R_RISCV_ADD64 a 0x0
+# CHECK-NEXT: 0x0 R_RISCV_SUB64 z 0x0
+# CHECK: }
+# CHECK: ]
+
+ .section sx,"aw", at progbits
+x:
+ .quad y-x
+
+ .section sy,"aw", at progbits
+y:
+ .quad x-y
+
+ .section sz
+z:
+ .quad z-a
+
+ .section sa
+a:
+ .quad a-z
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