[RuntimeDyldChecker][AArch32] Add a PC offset to next_PC for ARM targets

In ARM mode, the Program Counter (PC) points to the current instruction's
address + 8 instead of + 4. This offset is added to RuntimeDyldChecker to
use `next_pc` expression in JITLink tests.

Author: eymay

llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldChecker.cpp

@@ -369,7 +369,19 @@ class RuntimeDyldCheckerExprEval {
     uint64_t SymbolAddr = PCtx.IsInsideLoad
                               ? Checker.getSymbolLocalAddr(Symbol)
                               : Checker.getSymbolRemoteAddr(Symbol);
-    uint64_t NextPC = SymbolAddr + InstSize;
+
+    uint64_t PCOffset = 0;
+    auto TT = Checker.getTripleForSymbol(Checker.getTargetFlag(Symbol));
+    switch (TT.getArch()) {
+    case Triple::ArchType::arm:
+      // ARM mode adds an offset of 4 bytes to PC
+      PCOffset = 4;
+      break;
+    default:
+      PCOffset = 0;
+    }
+
+    uint64_t NextPC = SymbolAddr + InstSize + PCOffset;
 
     return std::make_pair(EvalResult(NextPC), RemainingExpr);
   }

llvm/test/ExecutionEngine/JITLink/AArch32/ELF_relocations_arm.s

@@ -28,9 +28,7 @@
 # CHECK-INSTR: 	       4: ebfffffe     bl
 # CHECK-INSTR: 	0000000c <call_target_arm>
 # CHECK-INSTR: 	00000010 <call_target_thumb>
-# ARM branch offset is 8, because it accounts for an additional prefetch
-# instruction that increments PC even though it is implicit
-# jitlink-check: decode_operand(call_site + 0, 0) = call_target_arm   - (call_site +  8)
+# jitlink-check: decode_operand(call_site + 0, 0) = call_target_arm   - next_pc(call_site)
 # jitlink-check: decode_operand(call_site + 4, 0) = call_target_thumb - (call_site + 12)
 	.globl	call_site
 	.type	call_site,%function
@@ -62,7 +60,7 @@ call_target_thumb:
 # CHECK-INSTR: 	00000014 <jump24_site>:
 # CHECK-INSTR: 	      14: eafffffe     b
 # CHECK-INSTR: 	00000018 <jump24_target>
-# jitlink-check: decode_operand(jump24_site, 0) = jump24_target - (jump24_site + 8)
+# jitlink-check: decode_operand(jump24_site, 0) = jump24_target - next_pc(jump24_site)
 	.globl	jump24_site
 	.type	jump24_site,%function
 	.p2align	2

llvm/test/ExecutionEngine/JITLink/AArch32/ELF_relocations_thumbv6m.s

@@ -30,7 +30,7 @@
 # CHECK-INSTR: f7ff fffe     bl
 # We decode the operand with index 2, because bl generates two leading implicit
 # predicate operands that we have to skip in order to decode the call_target operand
-# jitlink-check: decode_operand(call_site, 2) = call_target_thumb - (call_site + 4)
+# jitlink-check: decode_operand(call_site, 2) = call_target_thumb - next_pc(call_site)
 	.globl	call_site
 	.type	call_site,%function
 	.p2align	1