[PPC64] Fix offset checks on rel24 call relocations.

[sfertile]

Summary

Adjust the range check on a call instruction from 24 bits signed to 26 bits signed, and check that the target VA is 4 byte aligned. While the call instruction only encodes 24 bits of offset, the target address is implicitly assumed to be at least 4 byte aligned , giving the call instruction a reach of 26 signed bits.

[ruiu]

LGTM

lld/trunk/ELF/Arch/PPC64.cpp

case R_PPC64_REL32:
     break;
   case R_PPC64_ADDR64:
   case R_PPC64_REL64:
   case R_PPC64_TOC:
     write64(Loc, Val);
     break;
   case R_PPC64_REL24: {
     uint32_t Mask = 0x03FFFFFC;
-    checkInt(Loc, Val, 24, Type);
+    checkInt(Loc, Val, 26, Type);
+    checkAlignment(Loc, Val, 4, Type);
     write32(Loc, (read32(Loc) & ~Mask) | (Val & Mask));
     break;
   }
   case R_PPC64_DTPREL64:
     write64(Loc, Val - DynamicThreadPointerOffset);
     break;
   default:
     error(getErrorLocation(Loc) + "unrecognized reloc " + Twine(Type));

lld/trunk/test/ELF/ppc64-call-reach.s

+# REQUIRES: ppc
+
+# RUN: llvm-mc -filetype=obj -triple=powerpc64le-unknown-linux %s -o %t.o
+# RUN: ld.lld --defsym callee=0x12010010 --defsym tail_callee=0x12010020 \
+# RUN: %t.o -o %t
+# RUN: llvm-objdump -d %t | FileCheck %s
+# RUN: ld.lld --defsym callee=0x12010010 --defsym tail_callee=0x12010020 \
+# RUN: %t.o -o %t
+# RUN: llvm-objdump -d %t | FileCheck %s
+# RUN: ld.lld --defsym callee=0xE010014 --defsym tail_callee=0xE010024 \
+# RUN: %t.o -o %t
+# RUN: llvm-objdump -d %t | FileCheck --check-prefix=NEGOFFSET  %s
+# RUN: not ld.lld --defsym callee=0x12010018 --defsym tail_callee=0x12010028 \
+# RUN: %t.o -o %t 2>&1 | FileCheck --check-prefix=OVERFLOW %s
+# RUN: not ld.lld --defsym callee=0x1001002D --defsym tail_callee=0x1001002F \
+# RUN: %t.o -o %t 2>&1 | FileCheck --check-prefix=MISSALIGNED %s
+
+# RUN: llvm-mc -filetype=obj -triple=powerpc64-unknown-linux %s -o %t.o
+# RUN: ld.lld --defsym callee=0x12010010 --defsym tail_callee=0x12010020 \
+# RUN: %t.o -o %t
+# RUN: llvm-objdump -d %t | FileCheck %s
+# RUN: ld.lld --defsym callee=0x12010010 --defsym tail_callee=0x12010020 \
+# RUN: %t.o -o %t
+# RUN: llvm-objdump -d %t | FileCheck %s
+# RUN: ld.lld --defsym callee=0xE010014 --defsym tail_callee=0xE010024 \
+# RUN: %t.o -o %t
+# RUN: llvm-objdump -d %t | FileCheck --check-prefix=NEGOFFSET  %s
+# RUN: not ld.lld --defsym callee=0x12010018 --defsym tail_callee=0x12010028 \
+# RUN: %t.o -o %t 2>&1 | FileCheck --check-prefix=OVERFLOW %s
+# RUN: not ld.lld --defsym callee=0x1001002D --defsym tail_callee=0x1001002F \
+# RUN: %t.o -o %t 2>&1 | FileCheck --check-prefix=MISSALIGNED %s
+
+# OVERFLOW: ld.lld: error: {{.*}}.o:(.text+0x14): relocation R_PPC64_REL24 out of range: 33554436 is not in [-33554432, 33554431]
+# OVERFLOW: ld.lld: error: {{.*}}.o:(.text+0x24): relocation R_PPC64_REL24 out of range: 33554436 is not in [-33554432, 33554431]
+
+# MISSALIGNED: ld.lld: error: {{.*}}.o:(.text+0x14): improper alignment for relocation R_PPC64_REL24: 0x19 is not aligned to 4 bytes
+# MISSALIGNED: ld.lld: error: {{.*}}.o:(.text+0x24): improper alignment for relocation R_PPC64_REL24: 0xB is not aligned to 4 bytes
+
+        .global test
+        .p2align        4
+        .type   test,@function
+test:
+.Lgep:
+        addis 2, 12, .TOC.-.Lgep@ha
+        addi  2, 2,  .TOC.-.Lgep@l
+.Llep:
+        .localentry test, .Llep-.Lgep
+        mflr 0
+        std 0, 16(1)
+        stdu 1, 32(1)
+        bl callee
+        addi 1, 1, 32
+        ld 0, 16(1)
+        mtlr 0
+        b tail_callee
+
+# Check that we are branching to the definitions, and not range-extending
+# thunks.
+# CHECK-LABEL: test
+# CHECK:  10010014: {{.*}}  bl .+33554428
+# CHECK:  10010024: {{.*}}  b  .+33554428
+
+# NEGOFFSET-LABEL: test
+# NEGOFFSET:  10010014: {{.*}}  bl .+33554432
+# NEGOFFSET:  10010024: {{.*}}  b  .+33554432
+