Subzero: Transform suitable Load/Arith/Store sequences into RMW ops.

tests_lit/llvm2ice_tests/rmw.ll

+; This tests Read-Modify-Write (RMW) detection and lowering at the O2
+; optimization level.
+
+; RUN: %if --need=target_X8632 --command %p2i --filetype=obj --disassemble \
+; RUN:   --target x8632 -i %s --args -O2 \
+; RUN:   | %if --need=target_X8632 --command FileCheck %s
+
+define internal void @rmw_add_i32_var(i32 %addr_arg, i32 %var) {
+entry:
+  %addr = inttoptr i32 %addr_arg to i32*
+  %val = load i32, i32* %addr, align 1
+  %rmw = add i32 %val, %var
+  store i32 %rmw, i32* %addr, align 1
+  ret void
+}
+; Look for something like: add DWORD PTR [eax],ecx
+; CHECK-LABEL: rmw_add_i32_var
+; CHECK: add DWORD PTR [e{{ax|bx|cx|dx|bp|di|si}}],e{{ax|bx|cx|dx|bp|di|si}}
+
+define internal void @rmw_add_i32_imm(i32 %addr_arg) {
+entry:
+  %addr = inttoptr i32 %addr_arg to i32*
+  %val = load i32, i32* %addr, align 1
+  %rmw = add i32 %val, 19
+  store i32 %rmw, i32* %addr, align 1
+  ret void
+}
+; Look for something like: add DWORD PTR [eax],0x13
+; CHECK-LABEL: rmw_add_i32_imm
+; CHECK: add DWORD PTR [e{{ax|bx|cx|dx|bp|di|si}}],0x13
+
+define internal i32 @no_rmw_add_i32_var(i32 %addr_arg, i32 %var) {
+entry:
+  %addr = inttoptr i32 %addr_arg to i32*
+  %val = load i32, i32* %addr, align 1
+  %rmw = add i32 %val, %var
+  store i32 %rmw, i32* %addr, align 1
+  ret i32 %rmw
+}
+; CHECK-LABEL: no_rmw_add_i32_var
+; CHECK: add e{{ax|bx|cx|dx|bp|di|si}},DWORD PTR [e{{ax|bx|cx|dx|bp|di|si}}]
+
+define internal void @rmw_add_i16_var(i32 %addr_arg, i16 %var) {
+entry:
+  %addr = inttoptr i32 %addr_arg to i16*
+  %val = load i16, i16* %addr, align 1
+  %rmw = add i16 %val, %var
+  store i16 %rmw, i16* %addr, align 1
+  ret void
+}
+; Look for something like: add WORD PTR [eax],cx
+; CHECK-LABEL: rmw_add_i16_var
+; CHECK: add WORD PTR [e{{ax|bx|cx|dx|bp|di|si}}],{{ax|bx|cx|dx|bp|di|si}}
+
+define internal void @rmw_add_i16_imm(i32 %addr_arg) {
+entry:
+  %addr = inttoptr i32 %addr_arg to i16*
+  %val = load i16, i16* %addr, align 1
+  %rmw = add i16 %val, 19
+  store i16 %rmw, i16* %addr, align 1
+  ret void
+}
+; Look for something like: add WORD PTR [eax],0x13
+; CHECK-LABEL: rmw_add_i16_imm
+; CHECK: add WORD PTR [e{{ax|bx|cx|dx|bp|di|si}}],0x13
+
+define internal void @rmw_add_i8_var(i32 %addr_arg, i8 %var) {
+entry:
+  %addr = inttoptr i32 %addr_arg to i8*
+  %val = load i8, i8* %addr, align 1
+  %rmw = add i8 %val, %var
+  store i8 %rmw, i8* %addr, align 1
+  ret void
+}
+; Look for something like: add BYTE PTR [eax],cl
+; CHECK-LABEL: rmw_add_i8_var
+; CHECK: add BYTE PTR [e{{ax|bx|cx|dx|bp|di|si}}],{{al|bl|cl|dl}}
+
+define internal void @rmw_add_i8_imm(i32 %addr_arg) {
+entry:
+  %addr = inttoptr i32 %addr_arg to i8*
+  %val = load i8, i8* %addr, align 1
+  %rmw = add i8 %val, 19
+  store i8 %rmw, i8* %addr, align 1
+  ret void
+}
+; Look for something like: add BYTE PTR [eax],0x13
+; CHECK-LABEL: rmw_add_i8_imm
+; CHECK: add BYTE PTR [e{{ax|bx|cx|dx|bp|di|si}}],0x13
+
+define internal void @rmw_add_i32_var_addropt(i32 %addr_arg, i32 %var) {
+entry:
+  %addr_arg_plus_12 = add i32 %addr_arg, 12
+  %var_times_4 = mul i32 %var, 4
+  %addr_base = add i32 %addr_arg_plus_12 , %var_times_4
+  %addr = inttoptr i32 %addr_base to i32*
+  %val = load i32, i32* %addr, align 1
+  %rmw = add i32 %val, %var
+  store i32 %rmw, i32* %addr, align 1
+  ret void
+}
+; Look for something like: add DWORD PTR [eax+ecx*4+12],ecx
+; CHECK-LABEL: rmw_add_i32_var_addropt
+; CHECK: add DWORD PTR [e{{..}}+e{{..}}*4+0xc],e{{ax|bx|cx|dx|bp|di|si}}