[SystemZ] Make the CCRegs regclass non-allocatable.

This was discovered to be necessary while running memchr-01.ll with
-verify-machinstrs, because it is not allowed to have a phys reg live
accross block boundaries while on SSA form, if the register is
allocatable (expect in entry block and landing pads).

In this test case, stringRRE pseudos are expanded after isel by adding
a loop block which produces a live out CC register. To make the test
pass, it was also necessary to not say that StringRRELoop pseudo uses
R0L, this is only true for the StringRRE opcode.

-verify-machineinstrs added to memchr-01.ll test.

New test case int-cmp-51.ll to test that MachineCSE can eliminate
an identical compare (which it couldn't do before).

Reviewed by Ulrich Weigand

llvm-svn: 251634

llvm/lib/Target/SystemZ/SystemZInstrFormats.td

@@ -2381,6 +2381,7 @@ multiclass StringRRE<string mnemonic, bits<16> opcode,
   def "" : InstRRE<opcode, (outs GR64:$R1, GR64:$R2),
                    (ins GR64:$R1src, GR64:$R2src),
                    mnemonic#"\t$R1, $R2", []> {
+    let Uses = [R0L];
     let Constraints = "$R1 = $R1src, $R2 = $R2src";
     let DisableEncoding = "$R1src, $R2src";
   }

llvm/lib/Target/SystemZ/SystemZInstrInfo.td

@@ -397,7 +397,7 @@ let mayLoad = 1, mayStore = 1 in
   defm MVC : MemorySS<"mvc", 0xD2, z_mvc, z_mvc_loop>;
 
 // String moves.
-let mayLoad = 1, mayStore = 1, Defs = [CC], Uses = [R0L] in
+let mayLoad = 1, mayStore = 1, Defs = [CC] in
   defm MVST : StringRRE<"mvst", 0xB255, z_stpcpy>;
 
 //===----------------------------------------------------------------------===//
@@ -1185,7 +1185,7 @@ let mayLoad = 1, Defs = [CC] in
   defm CLC : MemorySS<"clc", 0xD5, z_clc, z_clc_loop>;
 
 // String comparison.
-let mayLoad = 1, Defs = [CC], Uses = [R0L] in
+let mayLoad = 1, Defs = [CC] in
   defm CLST : StringRRE<"clst", 0xB25D, z_strcmp>;
 
 // Test under mask.
@@ -1459,7 +1459,7 @@ let usesCustomInserter = 1 in {
 }
 
 // Search a block of memory for a character.
-let mayLoad = 1, Defs = [CC], Uses = [R0L] in
+let mayLoad = 1, Defs = [CC] in
   defm SRST : StringRRE<"srst", 0xb25e, z_search_string>;
 
 // Other instructions for inline assembly

llvm/lib/Target/SystemZ/SystemZRegisterInfo.td

@@ -282,4 +282,5 @@ def v128any : TypedReg<untyped, VR128>;
 // The 2-bit condition code field of the PSW.  Every register named in an
 // inline asm needs a class associated with it.
 def CC : SystemZReg<"cc">;
-def CCRegs : RegisterClass<"SystemZ", [i32], 32, (add CC)>;
+let isAllocatable = 0 in
+  def CCRegs : RegisterClass<"SystemZ", [i32], 32, (add CC)>;

llvm/test/CodeGen/SystemZ/int-cmp-51.ll

@@ -0,0 +1,34 @@
+; Check that modelling of CC/CCRegs does not stop MachineCSE from
+; removing a compare.  MachineCSE will not extend a live range of an
+; allocatable or reserved phys reg.
+;
+; RUN: llc < %s -mtriple=s390x-linux-gnu | FileCheck %s
+
+declare void @bar(i8)
+
+; Check the low end of the CH range.
+define void @f1(i32 %lhs) {
+; CHECK-LABEL: BB#1:
+; CHECK-NOT: cijlh %r0, 1, .LBB0_3
+
+entry:
+  %and188 = and i32 %lhs, 255
+  %cmp189 = icmp ult i32 %and188, 2
+  br i1 %cmp189, label %if.then.191, label %if.else.201
+
+if.then.191:
+  %cmp194 = icmp eq i32 %and188, 1
+  br i1 %cmp194, label %if.then.196, label %if.else.198
+
+if.then.196:
+  call void @bar(i8 1);
+  br label %if.else.201
+
+if.else.198:
+  call void @bar(i8 0);
+  br label %if.else.201
+
+if.else.201:
+  ret void
+}
+

llvm/test/CodeGen/SystemZ/memchr-01.ll

@@ -1,6 +1,6 @@
 ; Test memchr using SRST, with a weird but usable prototype.
 ;
-; RUN: llc < %s -mtriple=s390x-linux-gnu | FileCheck %s
+; RUN: llc < %s -mtriple=s390x-linux-gnu -verify-machineinstrs | FileCheck %s
 
 declare i8 *@memchr(i8 *%src, i16 %char, i32 %len)