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[Hexagon] Separate C8 and USR to avoid unwanted subregister composition 

Composing subreg_loreg with subreg_oveflow leads to strange results with
lane masks for register classes with subreg_loreg. In particular, dead
lane detection generates incorrect code.

llvm-svn: 271087
This commit is contained in:
Krzysztof Parzyszek 2016-05-28 01:51:16 +00:00
parent d69cd1e086
commit 96bb4fe539
2 changed files with 18 additions and 6 deletions
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19
llvm/lib/Target/Hexagon/HexagonRegisterInfo.td
View File

@ -132,6 +132,11 @@ let Namespace = "Hexagon" in {
// on the entire USR.
def USR_OVF : Rc<?, "usr.ovf">;
def USR : Rc<8, "usr", ["c8"]>, DwarfRegNum<[75]> {
let SubRegIndices = [subreg_overflow];
let SubRegs = [USR_OVF];
}
// Control registers.
def SA0 : Rc<0, "sa0", ["c0"]>, DwarfRegNum<[67]>;
def LC0 : Rc<1, "lc0", ["c1"]>, DwarfRegNum<[68]>;
@ -142,11 +147,12 @@ let Namespace = "Hexagon" in {
def C5 : Rc<5, "c5", ["c5"]>, DwarfRegNum<[72]>; // future use
def C6 : Rc<6, "c6", [], [M0]>, DwarfRegNum<[73]>;
def C7 : Rc<7, "c7", [], [M1]>, DwarfRegNum<[74]>;
def USR : Rc<8, "usr", ["c8"]>, DwarfRegNum<[75]> {
let SubRegIndices = [subreg_overflow];
let SubRegs = [USR_OVF];
}
// Define C8 separately and make it aliased with USR.
// The problem is that USR has subregisters (e.g. overflow). If USR was
// specified as a subregister of C9_8, it would imply that subreg_overflow
// and subreg_loreg can be composed, which leads to all kinds of issues
// with lane masks.
def C8 : Rc<8, "c8", [], [USR]>, DwarfRegNum<[75]>;
def PC : Rc<9, "pc">, DwarfRegNum<[76]>;
def UGP : Rc<10, "ugp", ["c10"]>, DwarfRegNum<[77]>;
def GP : Rc<11, "gp">, DwarfRegNum<[78]>;
@ -161,7 +167,8 @@ let Namespace = "Hexagon" in {
def C1_0 : Rcc<0, "c1:0", [SA0, LC0], ["lc0:sa0"]>, DwarfRegNum<[67]>;
def C3_2 : Rcc<2, "c3:2", [SA1, LC1], ["lc1:sa1"]>, DwarfRegNum<[69]>;
def C7_6 : Rcc<6, "c7:6", [C6, C7], ["m1:0"]>, DwarfRegNum<[72]>;
def C9_8 : Rcc<8, "c9:8", [USR, PC]>, DwarfRegNum<[74]>;
// Use C8 instead of USR as a subregister of C9_8.
def C9_8 : Rcc<8, "c9:8", [C8, PC]>, DwarfRegNum<[74]>;
def C11_10 : Rcc<10, "c11:10", [UGP, GP]>, DwarfRegNum<[76]>;
def CS : Rcc<12, "c13:12", [CS0, CS1], ["cs1:0"]>, DwarfRegNum<[78]>;
def UPC : Rcc<14, "c15:14", [UPCL, UPCH]>, DwarfRegNum<[80]>;

5
llvm/lib/Target/Hexagon/MCTargetDesc/HexagonMCChecker.cpp
View File

@ -116,6 +116,11 @@ void HexagonMCChecker::init(MCInst const& MCI) {
for (unsigned i = 0; i < MCID.getNumDefs(); ++i) {
unsigned R = MCI.getOperand(i).getReg(),
S = Hexagon::NoRegister;
// USR has subregisters (while C8 does not for technical reasons), so
// reset R to USR, since we know how to handle multiple defs of USR,
// taking into account its subregisters.
if (R == Hexagon::C8)
R = Hexagon::USR;
// Note register definitions, direct ones as well as indirect side-effects.
// Super-registers are not tracked directly, but their components.