diff --git a/lld/ELF/InputSection.cpp b/lld/ELF/InputSection.cpp
--- a/lld/ELF/InputSection.cpp
+++ b/lld/ELF/InputSection.cpp
@@ -979,6 +979,52 @@
       }
       target->relocateOne(bufLoc, type, targetVA);
       break;
+    case R_PC:
+      if (config->emachine == EM_RISCV && rel.sym->isUndefWeak() &&
+          !config->isPic) {
+        // Patch addresses of undefined weak symbols to be NULL.
+        if (rel.addend != 0)
+          error(getErrorLocation(bufLoc) +
+                "undefined weak symbol relocation with non-zero addend");
+        uint32_t insn = read32le(bufLoc);
+        switch (type) {
+        case R_RISCV_CALL:
+          // Clear immediate in following jalr.
+          write32le(bufLoc + 4, read32le(bufLoc + 4) & 0x000fffff);
+          LLVM_FALLTHROUGH;
+        case R_RISCV_PCREL_HI20:
+          // Rewrite auipc rd, %pcrel_hi(sym) to lui rd, 0.
+          write32le(bufLoc, (insn & 0x00000f80) | 0x00000037);
+          break;
+        case R_RISCV_JAL:
+          write32le(bufLoc, insn & 0x00000fff);
+          break;
+        case R_RISCV_BRANCH:
+          error(getErrorLocation(bufLoc) +
+                "conditional branch to undefined weak symbol '" +
+                rel.sym->getName() + "'");
+          break;
+        default:
+          error(getErrorLocation(bufLoc) +
+                "unknown RISC-V relocation " + toString(type) +
+                " for undefined weak symbol");
+          break;
+        }
+        break;
+      }
+      target->relocateOne(bufLoc, type, targetVA);
+      break;
+    case R_RISCV_PC_INDIRECT:
+      if (!config->isPic) {
+        const Relocation *hiRel = getRISCVPCRelHi20(rel.sym, rel.addend);
+        if (hiRel && hiRel->type == R_RISCV_PCREL_HI20
+            && hiRel->sym->isUndefWeak() && hiRel->addend == 0) {
+          // Patch addresses of undefined weak symbols to be NULL.
+          targetVA = 0;
+        }
+      }
+      target->relocateOne(bufLoc, type, targetVA);
+      break;
     default:
       target->relocateOne(bufLoc, type, targetVA);
       break;
diff --git a/lld/test/ELF/riscv-undefined-weak-branch.s b/lld/test/ELF/riscv-undefined-weak-branch.s
new file mode 100644
--- /dev/null
+++ b/lld/test/ELF/riscv-undefined-weak-branch.s
@@ -0,0 +1,15 @@
+// REQUIRES: riscv
+// RUN: llvm-mc -filetype=obj -triple=riscv64-none-linux %s -o %t.o
+// RUN: not ld.lld %t.o -o /dev/null 2>&1 | FileCheck %s
+
+// Check that we don't permit conditional branches to undefined weak
+// symbols in non-PIC code.
+	
+ .weak target
+
+ .text
+ .global _start
+_start:
+ beq a0, a1, target
+
+// CHECK: error: {{.*}}: conditional branch to undefined weak symbol 'target'
diff --git a/lld/test/ELF/riscv-undefined-weak.s b/lld/test/ELF/riscv-undefined-weak.s
new file mode 100644
--- /dev/null
+++ b/lld/test/ELF/riscv-undefined-weak.s
@@ -0,0 +1,42 @@
+// REQUIRES: riscv
+// RUN: llvm-mc -filetype=obj -triple=riscv64-none-linux %s -o %t.o
+// RUN: ld.lld %t.o -o %t
+// RUN: llvm-objdump -d --no-show-raw-insn %t | FileCheck %s
+
+// Check that undefined weak symbols are resolved to NULL in non-PIC
+// RISC-V code.
+	
+ .weak target
+
+ .text
+ .global _start
+_start:
+// R_RISCV_PCREL_HI20 + R_RISCV_LO12_I
+ la a0, target
+// R_RISCV_PCREL_HI20 + R_RISCV_LO12_I
+ ld a1, target
+// R_RISCV_PCREL_HI20 + R_RISCV_LO12_S
+ sd a2, target, t0
+// R_RISCV_JAL
+ j target
+// R_RISCV_JAL
+ jal target
+// R_RISCV_CALL
+ call target
+// R_RISCV_CALL
+ tail target
+
+// CHECK: Disassembly of section .text:
+// CHECK-EMPTY:
+// CHECK:         11120:      	lui	a0, 0
+// CHECK-NEXT:    11124:      	mv	a0, a0
+// CHECK:         11128:      	lui	a1, 0
+// CHECK-NEXT:    1112c:      	ld	a1, 0(a1)
+// CHECK:         11130:      	lui	t0, 0
+// CHECK-NEXT:    11134:      	sd	a2, 0(t0)
+// CHECK-NEXT:    11138:      	j	0
+// CHECK-NEXT:    1113c:      	jal	0
+// CHECK-NEXT:    11140:      	lui	ra, 0
+// CHECK-NEXT:    11144:      	jalr	ra
+// CHECK-NEXT:    11148:      	lui	t1, 0
+// CHECK-NEXT:    1114c:      	jr	t1