[llvm] [PowerPC][EarlyIfConversion] Do not insert `isel` if subtarget doesn't support `isel` (PR #72211)

[Kai Luo via llvm-commits]

https://github.com/bzEq created https://github.com/llvm/llvm-project/pull/72211

Some subtargets of PPC doesn't support `isel` instruction, early-ifcvt should not insert this instruction.

>From af987082dfddc56961405a133b21065138cefd4b Mon Sep 17 00:00:00 2001
From: Kai Luo <lkail at cn.ibm.com>
Date: Tue, 14 Nov 2023 05:39:07 +0000
Subject: [PATCH 1/3] [PowerPC] Precommit test to show impact of early-ifcvt on
 target without `isel`. NFC.

---
 llvm/test/CodeGen/PowerPC/early-ifcvt-no-isel.mir | 2 --
 1 file changed, 2 deletions(-)

diff --git a/llvm/test/CodeGen/PowerPC/early-ifcvt-no-isel.mir b/llvm/test/CodeGen/PowerPC/early-ifcvt-no-isel.mir
index 56cfef672ebf574..39396c264c51865 100644
--- a/llvm/test/CodeGen/PowerPC/early-ifcvt-no-isel.mir
+++ b/llvm/test/CodeGen/PowerPC/early-ifcvt-no-isel.mir
@@ -45,8 +45,6 @@ body:             |
   ; CHECK-NEXT:   [[ADDI:%[0-9]+]]:gprc_and_gprc_nor0 = nsw ADDI [[LWZ]], 1
   ; CHECK-NEXT:   [[CMPWI:%[0-9]+]]:crrc = CMPWI [[LWZ]], 750
   ; CHECK-NEXT:   [[LI:%[0-9]+]]:gprc_and_gprc_nor0 = LI 1
-  ; CHECK-NEXT:   [[ISEL:%[0-9]+]]:gprc = ISEL [[ADDI]], [[LI]], [[CMPWI]].sub_lt
-  ; CHECK-NEXT:   STW killed [[ISEL]], 0, [[COPY]] :: (store (s32) into %ir.dummy)
   ; CHECK-NEXT:   [[LI8_:%[0-9]+]]:g8rc = LI8 0
   ; CHECK-NEXT:   $x3 = COPY [[LI8_]]
   ; CHECK-NEXT:   BLR8 implicit $lr8, implicit $rm, implicit $x3

>From 24f37ee9ef22b8650d266349faabe054b821b627 Mon Sep 17 00:00:00 2001
From: Kai Luo <lkail at cn.ibm.com>
Date: Tue, 14 Nov 2023 05:35:10 +0000
Subject: [PATCH 2/3] Up

---
 llvm/lib/Target/PowerPC/PPCInstrInfo.cpp | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp b/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp
index e1bb2f72657f8f0..c9e094a1588500c 100644
--- a/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp
+++ b/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp
@@ -1530,6 +1530,9 @@ bool PPCInstrInfo::canInsertSelect(const MachineBasicBlock &MBB,
                                    Register DstReg, Register TrueReg,
                                    Register FalseReg, int &CondCycles,
                                    int &TrueCycles, int &FalseCycles) const {
+  if (!Subtarget.hasISEL())
+    return false;
+
   if (Cond.size() != 2)
     return false;
 

>From fdee669969e717b4ce39da933b44b9916153f392 Mon Sep 17 00:00:00 2001
From: Kai Luo <lkail at cn.ibm.com>
Date: Tue, 14 Nov 2023 06:01:46 +0000
Subject: [PATCH 3/3] Up

---
 llvm/test/CodeGen/PowerPC/early-ifcvt-no-isel.mir | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/llvm/test/CodeGen/PowerPC/early-ifcvt-no-isel.mir b/llvm/test/CodeGen/PowerPC/early-ifcvt-no-isel.mir
index 39396c264c51865..99a3f80ff81b4d0 100644
--- a/llvm/test/CodeGen/PowerPC/early-ifcvt-no-isel.mir
+++ b/llvm/test/CodeGen/PowerPC/early-ifcvt-no-isel.mir
@@ -38,6 +38,7 @@ machineFunctionInfo: {}
 body:             |
   ; CHECK-LABEL: name: foo
   ; CHECK: bb.0.entry:
+  ; CHECK-NEXT:   successors: %bb.1, %bb.2
   ; CHECK-NEXT:   liveins: $x3
   ; CHECK-NEXT: {{  $}}
   ; CHECK-NEXT:   [[COPY:%[0-9]+]]:g8rc_and_g8rc_nox0 = COPY $x3
@@ -45,6 +46,13 @@ body:             |
   ; CHECK-NEXT:   [[ADDI:%[0-9]+]]:gprc_and_gprc_nor0 = nsw ADDI [[LWZ]], 1
   ; CHECK-NEXT:   [[CMPWI:%[0-9]+]]:crrc = CMPWI [[LWZ]], 750
   ; CHECK-NEXT:   [[LI:%[0-9]+]]:gprc_and_gprc_nor0 = LI 1
+  ; CHECK-NEXT:   BCC 12, [[CMPWI]], %bb.2
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT: bb.1.entry:
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT: bb.2.entry:
+  ; CHECK-NEXT:   [[PHI:%[0-9]+]]:gprc = PHI [[LI]], %bb.1, [[ADDI]], %bb.0
+  ; CHECK-NEXT:   STW killed [[PHI]], 0, [[COPY]] :: (store (s32) into %ir.dummy)
   ; CHECK-NEXT:   [[LI8_:%[0-9]+]]:g8rc = LI8 0
   ; CHECK-NEXT:   $x3 = COPY [[LI8_]]
   ; CHECK-NEXT:   BLR8 implicit $lr8, implicit $rm, implicit $x3