[ARM] Implement ISB memory barrier intrinsic

Adds support for __builtin_arm_isb. Also corrects DSB and ISB instructions
modelling by adding has-side-effects property.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@212276 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/IR/IntrinsicsARM.td

@@ -56,6 +56,7 @@ def int_arm_ldaexd : Intrinsic<[llvm_i32_ty, llvm_i32_ty], [llvm_ptr_ty]>;
 // Data barrier instructions
 def int_arm_dmb : GCCBuiltin<"__builtin_arm_dmb">, Intrinsic<[], [llvm_i32_ty]>;
 def int_arm_dsb : GCCBuiltin<"__builtin_arm_dsb">, Intrinsic<[], [llvm_i32_ty]>;
+def int_arm_isb : GCCBuiltin<"__builtin_arm_isb">, Intrinsic<[], [llvm_i32_ty]>;
 
 //===----------------------------------------------------------------------===//
 // VFP

lib/Target/ARM/ARMInstrInfo.td

@@ -4443,7 +4443,7 @@ def instsyncb_opt : Operand<i32> {
   let DecoderMethod = "DecodeInstSyncBarrierOption";
 }
 
-// memory barriers protect the atomic sequences
+// Memory barriers protect the atomic sequences
 let hasSideEffects = 1 in {
 def DMB : AInoP<(outs), (ins memb_opt:$opt), MiscFrm, NoItinerary,
                 "dmb", "\t$opt", [(int_arm_dmb (i32 imm0_15:$opt))]>,
@@ -4452,7 +4452,6 @@ def DMB : AInoP<(outs), (ins memb_opt:$opt), MiscFrm, NoItinerary,
   let Inst{31-4} = 0xf57ff05;
   let Inst{3-0} = opt;
 }
-}
 
 def DSB : AInoP<(outs), (ins memb_opt:$opt), MiscFrm, NoItinerary,
                 "dsb", "\t$opt", [(int_arm_dsb (i32 imm0_15:$opt))]>,
@@ -4464,12 +4463,13 @@ def DSB : AInoP<(outs), (ins memb_opt:$opt), MiscFrm, NoItinerary,
 
 // ISB has only full system option
 def ISB : AInoP<(outs), (ins instsyncb_opt:$opt), MiscFrm, NoItinerary,
-                "isb", "\t$opt", []>,
+                "isb", "\t$opt", [(int_arm_isb (i32 imm0_15:$opt))]>,
                 Requires<[IsARM, HasDB]> {
   bits<4> opt;
   let Inst{31-4} = 0xf57ff06;
   let Inst{3-0} = opt;
 }
+}
 
 let usesCustomInserter = 1, Defs = [CPSR] in {
 

lib/Target/ARM/ARMInstrThumb2.td

@@ -3209,27 +3209,28 @@ def t2MOVCCi32imm
 let hasSideEffects = 1 in {
 def t2DMB : T2I<(outs), (ins memb_opt:$opt), NoItinerary,
                 "dmb", "\t$opt", [(int_arm_dmb (i32 imm0_15:$opt))]>,
-                Requires<[HasDB]> {
+                Requires<[IsThumb, HasDB]> {
   bits<4> opt;
   let Inst{31-4} = 0xf3bf8f5;
   let Inst{3-0} = opt;
 }
-}
 
 def t2DSB : T2I<(outs), (ins memb_opt:$opt), NoItinerary,
                 "dsb", "\t$opt", [(int_arm_dsb (i32 imm0_15:$opt))]>,
-                Requires<[HasDB]> {
+                Requires<[IsThumb, HasDB]> {
   bits<4> opt;
   let Inst{31-4} = 0xf3bf8f4;
   let Inst{3-0} = opt;
 }
 
 def t2ISB : T2I<(outs), (ins instsyncb_opt:$opt), NoItinerary,
-                "isb", "\t$opt", []>, Requires<[HasDB]> {
+                "isb", "\t$opt", [(int_arm_isb (i32 imm0_15:$opt))]>,
+                Requires<[IsThumb, HasDB]> {
   bits<4> opt;
   let Inst{31-4} = 0xf3bf8f6;
   let Inst{3-0} = opt;
 }
+}
 
 class T2I_ldrex<bits<4> opcod, dag oops, dag iops, AddrMode am, int sz,
                 InstrItinClass itin, string opc, string asm, string cstr,

test/CodeGen/ARM/intrinsics-memory-barrier.ll

@@ -0,0 +1,55 @@
+; RUN: llc < %s -mtriple=armv7 -mattr=+db | FileCheck %s
+; RUN: llc < %s -mtriple=thumbv7 -mattr=+db | FileCheck %s
+
+; CHECK-LABEL: test
+define void @test() {
+  call void @llvm.arm.dmb(i32 3)     ; CHECK: dmb osh
+  call void @llvm.arm.dsb(i32 7)     ; CHECK: dsb nsh
+  call void @llvm.arm.isb(i32 15)    ; CHECK: isb sy
+  ret void
+}
+
+; Important point is that the compiler should not reorder memory access
+; instructions around DMB.
+; Failure to do so, two STRs will collapse into one STRD.
+; CHECK-LABEL: test_dmb_reordering
+define void @test_dmb_reordering(i32 %a, i32 %b, i32* %d) {
+  store i32 %a, i32* %d              ; CHECK: str {{r[0-9]+}}, [{{r[0-9]+}}]
+
+  call void @llvm.arm.dmb(i32 15)    ; CHECK: dmb sy
+
+  %d1 = getelementptr i32* %d, i32 1
+  store i32 %b, i32* %d1             ; CHECK: str {{r[0-9]+}}, [{{r[0-9]+}}, #4]
+
+  ret void
+}
+
+; Similarly for DSB.
+; CHECK-LABEL: test_dsb_reordering
+define void @test_dsb_reordering(i32 %a, i32 %b, i32* %d) {
+  store i32 %a, i32* %d              ; CHECK: str {{r[0-9]+}}, [{{r[0-9]+}}]
+
+  call void @llvm.arm.dsb(i32 15)    ; CHECK: dsb sy
+
+  %d1 = getelementptr i32* %d, i32 1
+  store i32 %b, i32* %d1             ; CHECK: str {{r[0-9]+}}, [{{r[0-9]+}}, #4]
+
+  ret void
+}
+
+; And ISB.
+; CHECK-LABEL: test_isb_reordering
+define void @test_isb_reordering(i32 %a, i32 %b, i32* %d) {
+  store i32 %a, i32* %d              ; CHECK: str {{r[0-9]+}}, [{{r[0-9]+}}]
+
+  call void @llvm.arm.isb(i32 15)    ; CHECK: isb sy
+
+  %d1 = getelementptr i32* %d, i32 1
+  store i32 %b, i32* %d1             ; CHECK: str {{r[0-9]+}}, [{{r[0-9]+}}, #4]
+
+  ret void
+}
+
+declare void @llvm.arm.dmb(i32)
+declare void @llvm.arm.dsb(i32)
+declare void @llvm.arm.isb(i32)