[llvm-branch-commits] [llvm] 80f974e - [AArch64][GlobalISel] Use ZExtValue for zext(xor) when invert tb(n)z

[Tom Stellard via llvm-branch-commits]

Author: guopeilin
Date: 2021-09-21T09:15:10-07:00
New Revision: 80f974e40f81348b1676247e832287da29dd02dd

URL: https://github.com/llvm/llvm-project/commit/80f974e40f81348b1676247e832287da29dd02dd
DIFF: https://github.com/llvm/llvm-project/commit/80f974e40f81348b1676247e832287da29dd02dd.diff

LOG: [AArch64][GlobalISel] Use ZExtValue for zext(xor) when invert tb(n)z

Currently, we use SExtValue to decide whether to invert tbz or tbnz.
However, for the case zext (xor x, c), we should use ZExt rather
than SExt otherwise we will generate totally opposite branches.

Reviewed By: paquette

Differential Revision: https://reviews.llvm.org/D108755

(cherry picked from commit 5f48c144c58f6d23e850a1978a6fe05887103b17)

Added: 
    

Modified: 
    llvm/lib/Target/AArch64/GISel/AArch64InstructionSelector.cpp
    llvm/test/CodeGen/AArch64/GlobalISel/opt-fold-xor-tbz-tbnz.mir

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Target/AArch64/GISel/AArch64InstructionSelector.cpp b/llvm/lib/Target/AArch64/GISel/AArch64InstructionSelector.cpp
index a98248438e401..a17bd1b14f412 100644
--- a/llvm/lib/Target/AArch64/GISel/AArch64InstructionSelector.cpp
+++ b/llvm/lib/Target/AArch64/GISel/AArch64InstructionSelector.cpp
@@ -1301,6 +1301,7 @@ static AArch64CC::CondCode changeICMPPredToAArch64CC(CmpInst::Predicate P) {
 static Register getTestBitReg(Register Reg, uint64_t &Bit, bool &Invert,
                               MachineRegisterInfo &MRI) {
   assert(Reg.isValid() && "Expected valid register!");
+  bool HasZext = false;
   while (MachineInstr *MI = getDefIgnoringCopies(Reg, MRI)) {
     unsigned Opc = MI->getOpcode();
 
@@ -1314,6 +1315,9 @@ static Register getTestBitReg(Register Reg, uint64_t &Bit, bool &Invert,
     // on the truncated x is the same as the bit number on x.
     if (Opc == TargetOpcode::G_ANYEXT || Opc == TargetOpcode::G_ZEXT ||
         Opc == TargetOpcode::G_TRUNC) {
+      if (Opc == TargetOpcode::G_ZEXT)
+        HasZext = true;
+
       Register NextReg = MI->getOperand(1).getReg();
       // Did we find something worth folding?
       if (!NextReg.isValid() || !MRI.hasOneNonDBGUse(NextReg))
@@ -1342,8 +1346,12 @@ static Register getTestBitReg(Register Reg, uint64_t &Bit, bool &Invert,
         std::swap(ConstantReg, TestReg);
         VRegAndVal = getConstantVRegValWithLookThrough(ConstantReg, MRI);
       }
-      if (VRegAndVal)
-        C = VRegAndVal->Value.getSExtValue();
+      if (VRegAndVal) {
+        if (HasZext)
+          C = VRegAndVal->Value.getZExtValue();
+        else
+          C = VRegAndVal->Value.getSExtValue();
+      }
       break;
     }
     case TargetOpcode::G_ASHR:

diff  --git a/llvm/test/CodeGen/AArch64/GlobalISel/opt-fold-xor-tbz-tbnz.mir b/llvm/test/CodeGen/AArch64/GlobalISel/opt-fold-xor-tbz-tbnz.mir
index 8e19ba41b2c0c..53ea6830fdc89 100644
--- a/llvm/test/CodeGen/AArch64/GlobalISel/opt-fold-xor-tbz-tbnz.mir
+++ b/llvm/test/CodeGen/AArch64/GlobalISel/opt-fold-xor-tbz-tbnz.mir
@@ -117,6 +117,38 @@ body:             |
     RET_ReallyLR
 ...
 ---
+name:            dont_flip_eq_zext
+alignment:       4
+legalized:       true
+regBankSelected: true
+tracksRegLiveness: true
+body:             |
+  ; CHECK-LABEL: name: dont_flip_eq_zext
+  ; CHECK: bb.0:
+  ; CHECK:   successors: %bb.0(0x40000000), %bb.1(0x40000000)
+  ; CHECK:   [[COPY:%[0-9]+]]:gpr32 = COPY $wzr
+  ; CHECK:   [[SUBREG_TO_REG:%[0-9]+]]:gpr64all = SUBREG_TO_REG 0, [[COPY]], %subreg.sub_32
+  ; CHECK:   [[COPY1:%[0-9]+]]:gpr64 = COPY [[SUBREG_TO_REG]]
+  ; CHECK:   TBNZX [[COPY1]], 63, %bb.1
+  ; CHECK:   B %bb.0
+  ; CHECK: bb.1:
+  ; CHECK:   RET_ReallyLR
+  bb.0:
+    successors: %bb.0(0x40000000), %bb.1(0x40000000)
+
+    %1:gpr(s32) = G_CONSTANT i32 0
+    %3:gpr(s32) = G_CONSTANT i32 -1
+    %4:gpr(s32) = G_XOR %1, %3
+    %5:gpr(s64) = G_ZEXT %4(s32)
+    %15:gpr(s64) = G_CONSTANT i64 0
+    %13:gpr(s32) = G_ICMP intpred(slt), %5(s64), %15
+    %7:gpr(s1) = G_TRUNC %13(s32)
+    G_BRCOND %7(s1), %bb.1
+    G_BR %bb.0
+  bb.1:
+    RET_ReallyLR
+...
+---
 name:            dont_flip_ne
 alignment:       4
 legalized:       true