ARM: fix Thumb2 CodeGen for ldrex with folded frame-index.

Because t2LDREX (& t2STREX) were marked as AddrModeNone, but did allow a
FrameIndex operand, rewriteT2FrameIndex asserted. This gives them a
proper addressing-mode and tells the rewriter about it so that encodable
offsets are exploited and others are rejected.

Should fix PR38828.

llvm-svn: 341642

5 files changed, 12 insertions, 3 deletions

diff --git a/llvm/lib/Target/ARM/ARMFrameLowering.cpp b/llvm/lib/Target/ARM/ARMFrameLowering.cpp
index 2f5701934a2..742d5dd3d8c 100644
--- a/llvm/lib/Target/ARM/ARMFrameLowering.cpp
+++ b/llvm/lib/Target/ARM/ARMFrameLowering.cpp
@@ -1516,6 +1516,7 @@ static unsigned estimateRSStackSizeLimit(MachineFunction &MF,
           break;
         case ARMII::AddrMode5:
         case ARMII::AddrModeT2_i8s4:
+        case ARMII::AddrModeT2_ldrex:
           Limit = std::min(Limit, ((1U << 8) - 1) * 4);
           break;
         case ARMII::AddrModeT2_i12:
diff --git a/llvm/lib/Target/ARM/ARMInstrFormats.td b/llvm/lib/Target/ARM/ARMInstrFormats.td
index 87a28023e97..0df48ba6129 100644
--- a/llvm/lib/Target/ARM/ARMInstrFormats.td
+++ b/llvm/lib/Target/ARM/ARMInstrFormats.td
@@ -109,6 +109,7 @@ def AddrModeT2_pc   : AddrMode<14>;
 def AddrModeT2_i8s4 : AddrMode<15>;
 def AddrMode_i12    : AddrMode<16>;
 def AddrMode5FP16   : AddrMode<17>;
+def AddrModeT2_ldrex : AddrMode<18>;
 
 // Load / store index mode.
 class IndexMode<bits<2> val> {
diff --git a/llvm/lib/Target/ARM/ARMInstrThumb2.td b/llvm/lib/Target/ARM/ARMInstrThumb2.td
index c0054815c00..95195e85c4e 100644
--- a/llvm/lib/Target/ARM/ARMInstrThumb2.td
+++ b/llvm/lib/Target/ARM/ARMInstrThumb2.td
@@ -3275,7 +3275,7 @@ def t2LDREXH : T2I_ldrex<0b0101, (outs rGPR:$Rt), (ins addr_offset_none:$addr),
                          [(set rGPR:$Rt, (ldrex_2 addr_offset_none:$addr))]>,
                Requires<[IsThumb, HasV8MBaseline]>;
 def t2LDREX  : Thumb2I<(outs rGPR:$Rt), (ins t2addrmode_imm0_1020s4:$addr),
-                       AddrModeNone, 4, NoItinerary,
+                       AddrModeT2_ldrex, 4, NoItinerary,
                        "ldrex", "\t$Rt, $addr", "",
                      [(set rGPR:$Rt, (ldrex_4 t2addrmode_imm0_1020s4:$addr))]>,
                Requires<[IsThumb, HasV8MBaseline]> {
@@ -3354,7 +3354,7 @@ def t2STREXH : T2I_strex<0b0101, (outs rGPR:$Rd),
 
 def t2STREX  : Thumb2I<(outs rGPR:$Rd), (ins rGPR:$Rt,
                              t2addrmode_imm0_1020s4:$addr),
-                  AddrModeNone, 4, NoItinerary,
+                  AddrModeT2_ldrex, 4, NoItinerary,
                   "strex", "\t$Rd, $Rt, $addr", "",
                   [(set rGPR:$Rd,
                         (strex_4 rGPR:$Rt, t2addrmode_imm0_1020s4:$addr))]>,
diff --git a/llvm/lib/Target/ARM/MCTargetDesc/ARMBaseInfo.h b/llvm/lib/Target/ARM/MCTargetDesc/ARMBaseInfo.h
index cdadf198e90..33c32d5464a 100644
--- a/llvm/lib/Target/ARM/MCTargetDesc/ARMBaseInfo.h
+++ b/llvm/lib/Target/ARM/MCTargetDesc/ARMBaseInfo.h
@@ -201,7 +201,8 @@ namespace ARMII {
     AddrModeT2_pc   = 14, // +/- i12 for pc relative data
     AddrModeT2_i8s4 = 15, // i8 * 4
     AddrMode_i12    = 16,
-    AddrMode5FP16   = 17  // i8 * 2
+    AddrMode5FP16   = 17,  // i8 * 2
+    AddrModeT2_ldrex = 18, // i8 * 4, with unscaled offset in MCInst
   };
 
   inline static const char *AddrModeToString(AddrMode addrmode) {
@@ -224,6 +225,7 @@ namespace ARMII {
     case AddrModeT2_pc:   return "AddrModeT2_pc";
     case AddrModeT2_i8s4: return "AddrModeT2_i8s4";
     case AddrMode_i12:    return "AddrMode_i12";
+    case AddrModeT2_ldrex:return "AddrModeT2_ldrex";
     }
   }
 
diff --git a/llvm/lib/Target/ARM/Thumb2InstrInfo.cpp b/llvm/lib/Target/ARM/Thumb2InstrInfo.cpp
index d5f0ba9ee48..1a91a703065 100644
--- a/llvm/lib/Target/ARM/Thumb2InstrInfo.cpp
+++ b/llvm/lib/Target/ARM/Thumb2InstrInfo.cpp
@@ -621,6 +621,11 @@ bool llvm::rewriteT2FrameIndex(MachineInstr &MI, unsigned FrameRegIdx,
       // MCInst operand expects already scaled value.
       Scale = 1;
       assert((Offset & 3) == 0 && "Can't encode this offset!");
+    } else if (AddrMode == ARMII::AddrModeT2_ldrex) {
+      Offset += MI.getOperand(FrameRegIdx + 1).getImm() * 4;
+      NumBits = 8; // 8 bits scaled by 4
+      Scale = 4;
+      assert((Offset & 3) == 0 && "Can't encode this offset!");
     } else {
       llvm_unreachable("Unsupported addressing mode!");
     }