WIP: [UpdateTestChecks] Add update test check support for fpmath metadata

[jmciver]

Summary

Part of a sequence of exploratory patches using poison semantics for
uninitialized memory.

Add fpmath metadata support to update test check utilities.

llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/basic-metadata.ll

+; Just run it through opt, no passes needed.
+; RUN: opt < %s -S | FileCheck %s
+
+define double @fpmathTest(double %a, double %b) {
+entry:
+  %ret = fmul double %a, %b, !fpmath !0
+  ret double %ret
+}
+
+!0 = !{float 3.0}

llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/basic-metadata.ll.expected

+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; Just run it through opt, no passes needed.
+; RUN: opt < %s -S | FileCheck %s
+
+define double @fpmathTest(double %a, double %b) {
+; CHECK-LABEL: @fpmathTest(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[RET:%.*]] = fmul double [[A:%.*]], [[B:%.*]], !fpmath [[FPMATH0:![0-9]+]]
+; CHECK-NEXT:    ret double [[RET]]
+;
+entry:
+  %ret = fmul double %a, %b, !fpmath !0
+  ret double %ret
+}
+
+!0 = !{float 3.0}

llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/basic-metadata.ll.globals.expected

+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --check-globals
+; Just run it through opt, no passes needed.
+; RUN: opt < %s -S | FileCheck %s
+
+define double @fpmathTest(double %a, double %b) {
+; CHECK-LABEL: @fpmathTest(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[RET:%.*]] = fmul double [[A:%.*]], [[B:%.*]], !fpmath [[FPMATH0:![0-9]+]]
+; CHECK-NEXT:    ret double [[RET]]
+;
+entry:
+  %ret = fmul double %a, %b, !fpmath !0
+  ret double %ret
+}
+
+!0 = !{float 3.0}
+;.
+; CHECK: [[FPMATH0]] = !{float 3.000000e+00}
+;.

llvm/test/tools/UpdateTestChecks/update_test_checks/basic-metadata.test

+## Basic test checking that update_test_checks.py differnt metadata
+# RUN: cp -f %S/Inputs/basic-metadata.ll %t.ll && %update_test_checks %t.ll
+# RUN: diff -u %t.ll %S/Inputs/basic-metadata.ll.expected
+## Check that running the script again does not change the result:
+# RUN: %update_test_checks %t.ll
+# RUN: diff -u %t.ll %S/Inputs/basic-metadata.ll.expected
+## Also try the --check-globals flag
+# RUN: %update_test_checks %t.ll --check-globals
+# RUN: diff -u %t.ll %S/Inputs/basic-metadata.ll.globals.expected

llvm/utils/UpdateTestChecks/common.py

ir_nameless_values = [
     NamelessValue(r"ATTR", "#", r"#", r"[0-9]+", None),
     NamelessValue(r"ATTR", "#", r"attributes #", r"[0-9]+", r"{[^}]*}"),
     NamelessValue(r"GLOB", "@", r"@", r"[0-9]+", None),
     NamelessValue(
         r"GLOB", "@", r"@", r'[a-zA-Z0-9_$"\\.-]+', r".+", is_before_functions=True
     ),
     NamelessValue(r"DBG", "!", r"!dbg ", r"![0-9]+", None),
     NamelessValue(r"DIASSIGNID", "!", r"!DIAssignID ", r"![0-9]+", None),
+    NamelessValue(r'FPMATH', '!', r'!fpmath ', r'![0-9]+', None),
     NamelessValue(r'FREEZE_BITS', '!', r'!freeze_bits ', r'![0-9]+', None),
     NamelessValue(r"PROF", "!", r"!prof ", r"![0-9]+", None),
     NamelessValue(r"TBAA", "!", r"!tbaa ", r"![0-9]+", None),
     NamelessValue(r"TBAA_STRUCT", "!", r"!tbaa.struct ", r"![0-9]+", None),
     NamelessValue(r"RNG", "!", r"!range ", r"![0-9]+", None),
     NamelessValue(r"LOOP", "!", r"!llvm.loop ", r"![0-9]+", None),
     NamelessValue(r"META", "!", r"metadata ", r"![0-9]+", None),
     NamelessValue(r"META", "!", r"", r"![0-9]+", r"(?:distinct |)!.*"),