Fixed a crasher in arm disassembler within ARMInstPrinter.cpp after calling

ARM_AM::getSoImmVal(V) with a legitimate so_imm value: #245 rotate right by 2.
Introduce ARM_AM::getSOImmValOneOrNoRotate(unsigned Arg) which is called from
ARMInstPrinter.cpp's printSOImm() function, replacing ARM_AM::getSOImmVal(V).

[12:44:43] johnny:/Volumes/data/llvm/git/trunk (local-trunk) $ gdb Debug/bin/llvm-mc
GNU gdb 6.3.50-20050815 (Apple version gdb-1346) (Fri Sep 18 20:40:51 UTC 2009)
Copyright 2004 Free Software Foundation, Inc.
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This GDB was configured as "x86_64-apple-darwin"...Reading symbols for shared libraries ... done

(gdb) set args  -triple=arm-apple-darwin9 -debug-only=arm-disassembler --disassemble
(gdb) r
Starting program: /Volumes/data/llvm/git/trunk/Debug/bin/llvm-mc -triple=arm-apple-darwin9 -debug-only=arm-disassembler --disassemble
Reading symbols for shared libraries ++. done
0xf5 0x71 0xf0 0x53
Opcode=201 Name=MVNi Format=ARM_FORMAT_DPFRM(4)
 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10  9  8  7  6  5  4  3  2  1  0 
-------------------------------------------------------------------------------------------------
| 0: 1: 0: 1| 0: 0: 1: 1| 1: 1: 1: 1| 0: 0: 0: 0| 0: 1: 1: 1| 0: 0: 0: 1| 1: 1: 1: 1| 0: 1: 0: 1|
-------------------------------------------------------------------------------------------------

	mvnpls	r7, Assertion failed: (V != -1 && "Not a valid so_imm value!"), function printSOImm, file ARMInstPrinter.cpp, line 229.

Program received signal SIGABRT, Aborted.
0x00007fff88c65886 in __kill ()
(gdb) bt
#0  0x00007fff88c65886 in __kill ()
#1  0x00007fff88d05eae in abort ()
#2  0x00007fff88cf2ef0 in __assert_rtn ()
#3  0x000000010020e422 in printSOImm (O=@0x1010bdf80, V=-1, VerboseAsm=false, MAI=0x1020106d0) at ARMInstPrinter.cpp:229
#4  0x000000010020e5fe in llvm::ARMInstPrinter::printSOImmOperand (this=0x1020107e0, MI=0x7fff5fbfee70, OpNum=1, O=@0x1010bdf80) at ARMInstPrinter.cpp:254
#5  0x00000001001ffbc0 in llvm::ARMInstPrinter::printInstruction (this=0x1020107e0, MI=0x7fff5fbfee70, O=@0x1010bdf80) at ARMGenAsmWriter.inc:3236
#6  0x000000010020c27c in llvm::ARMInstPrinter::printInst (this=0x1020107e0, MI=0x7fff5fbfee70, O=@0x1010bdf80) at ARMInstPrinter.cpp:182
#7  0x000000010003cbff in PrintInsts (DisAsm=@0x10200f4e0, Printer=@0x1020107e0, Bytes=@0x7fff5fbff060, SM=@0x7fff5fbff078) at Disassembler.cpp:65
#8  0x000000010003c8b4 in llvm::Disassembler::disassemble (T=@0x1010c13c0, Triple=@0x1010b6798, Buffer=@0x102010690) at Disassembler.cpp:153
#9  0x000000010004095c in DisassembleInput (ProgName=0x7fff5fbff3f0 "/Volumes/data/llvm/git/trunk/Debug/bin/llvm-mc") at llvm-mc.cpp:347
#10 0x000000010003eefb in main (argc=4, argv=0x7fff5fbff298) at llvm-mc.cpp:374
(gdb) q
The program is running.  Exit anyway? (y or n) y
[13:36:26] johnny:/Volumes/data/llvm/git/trunk (local-trunk) $ 


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@101053 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 41 insertions, 1 deletions

diff --git a/lib/Target/ARM/ARMAddressingModes.h b/lib/Target/ARM/ARMAddressingModes.h
index ea62c33..45b37b1 100644
--- a/lib/Target/ARM/ARMAddressingModes.h
+++ b/lib/Target/ARM/ARMAddressingModes.h
@@ -193,6 +193,43 @@ namespace ARM_AM {
     return rotl32(Arg, RotAmt) | ((RotAmt>>1) << 8);
   }
 
+  /// getSOImmValOneRotate - Try to handle Imm with an immediate shifter
+  /// operand, computing the rotate amount to use.  If this immediate value
+  /// cannot be handled with a single shifter-op, return 0.
+  static unsigned getSOImmValOneRotate(unsigned Imm) {
+    // A5.2.4 Constants with multiple encodings
+    // The lowest unsigned value of rotation wins!
+    for (unsigned R = 1; R <= 15; ++R)
+      if ((Imm & rotr32(~255U, 2*R)) == 0)
+        return 2*R;
+
+    // Failed to find a suitable rotate amount.
+    return 0;
+  }
+
+  /// getSOImmValOneOrNoRotate - Given a 32-bit immediate, if it is something
+  /// that can fit into a shifter_operand immediate operand, return the 12-bit
+  /// encoding for it.  If not, return -1.  This is different from getSOImmVal()
+  /// in that getSOImmVal() is used during codegen, for example,
+  /// rewriteARMFrameIndex() where return value of -1 is not considered fatal.
+  ///
+  /// The current consumer of this API is printSOImm() within ARMInstPrinter.cpp
+  /// where return value of -1 indicates that the Arg is not a valid so_imm val!
+  static inline int getSOImmValOneOrNoRotate(unsigned Arg) {
+    // 8-bit (or less) immediates are trivially shifter_operands with a rotate
+    // of zero.
+    if ((Arg & ~255U) == 0) return Arg;
+
+    unsigned RotAmt = getSOImmValOneRotate(Arg);
+
+    // If this cannot be handled with a single shifter_op, bail out.
+    if (rotr32(~255U, RotAmt) & Arg)
+      return -1;
+
+    // Encode this correctly.
+    return rotl32(Arg, RotAmt) | ((RotAmt>>1) << 8);
+  }
+
   /// isSOImmTwoPartVal - Return true if the specified value can be obtained by
   /// or'ing together two SOImmVal's.
   static inline bool isSOImmTwoPartVal(unsigned V) {
diff --git a/lib/Target/ARM/AsmPrinter/ARMInstPrinter.cpp b/lib/Target/ARM/AsmPrinter/ARMInstPrinter.cpp
index ef5ead6..c73fa13 100644
--- a/lib/Target/ARM/AsmPrinter/ARMInstPrinter.cpp
+++ b/lib/Target/ARM/AsmPrinter/ARMInstPrinter.cpp
@@ -225,7 +225,7 @@ void ARMInstPrinter::printOperand(const MCInst *MI, unsigned OpNo,
 static void printSOImm(raw_ostream &O, int64_t V, bool VerboseAsm,
                        const MCAsmInfo *MAI) {
   // Break it up into two parts that make up a shifter immediate.
-  V = ARM_AM::getSOImmVal(V);
+  V = ARM_AM::getSOImmValOneOrNoRotate(V);
   assert(V != -1 && "Not a valid so_imm value!");
   
   unsigned Imm = ARM_AM::getSOImmValImm(V);
diff --git a/test/MC/Disassembler/arm-tests.txt b/test/MC/Disassembler/arm-tests.txt
index 094a2d7..7d10107 100644
--- a/test/MC/Disassembler/arm-tests.txt
+++ b/test/MC/Disassembler/arm-tests.txt
@@ -27,6 +27,9 @@
 # CHECK:	movt	r8, #65535
 0xff 0x8f 0x4f 0xe3
 
+# CHECK:	mvnpls	r7, #245, 2
+0xf5 0x71 0xf0 0x53
+
 # CHECK:	pkhbt	r8, r9, r10, lsl #4
 0x1a 0x82 0x89 0xe6