github.com/gocuntian/go@v0.0.0-20160610041250-fee02d270bf8/src/cmd/compile/internal/gc/testdata/loadstore_ssa.go (about)

     1  // run
     2  
     3  // Copyright 2015 The Go Authors. All rights reserved.
     4  // Use of this source code is governed by a BSD-style
     5  // license that can be found in the LICENSE file.
     6  
     7  // Tests load/store ordering
     8  
     9  package main
    10  
    11  import "fmt"
    12  
    13  // testLoadStoreOrder tests for reordering of stores/loads.
    14  func testLoadStoreOrder() {
    15  	z := uint32(1000)
    16  	if testLoadStoreOrder_ssa(&z, 100) == 0 {
    17  		println("testLoadStoreOrder failed")
    18  		failed = true
    19  	}
    20  }
    21  
    22  //go:noinline
    23  func testLoadStoreOrder_ssa(z *uint32, prec uint) int {
    24  	old := *z         // load
    25  	*z = uint32(prec) // store
    26  	if *z < old {     // load
    27  		return 1
    28  	}
    29  	return 0
    30  }
    31  
    32  func testStoreSize() {
    33  	a := [4]uint16{11, 22, 33, 44}
    34  	testStoreSize_ssa(&a[0], &a[2], 77)
    35  	want := [4]uint16{77, 22, 33, 44}
    36  	if a != want {
    37  		fmt.Println("testStoreSize failed.  want =", want, ", got =", a)
    38  		failed = true
    39  	}
    40  }
    41  
    42  //go:noinline
    43  func testStoreSize_ssa(p *uint16, q *uint16, v uint32) {
    44  	// Test to make sure that (Store ptr (Trunc32to16 val) mem)
    45  	// does not end up as a 32-bit store. It must stay a 16 bit store
    46  	// even when Trunc32to16 is rewritten to be a nop.
    47  	// To ensure that we get rewrite the Trunc32to16 before
    48  	// we rewrite the Store, we force the truncate into an
    49  	// earlier basic block by using it on both branches.
    50  	w := uint16(v)
    51  	if p != nil {
    52  		*p = w
    53  	} else {
    54  		*q = w
    55  	}
    56  }
    57  
    58  var failed = false
    59  
    60  //go:noinline
    61  func testExtStore_ssa(p *byte, b bool) int {
    62  	x := *p
    63  	*p = 7
    64  	if b {
    65  		return int(x)
    66  	}
    67  	return 0
    68  }
    69  
    70  func testExtStore() {
    71  	const start = 8
    72  	var b byte = start
    73  	if got := testExtStore_ssa(&b, true); got != start {
    74  		fmt.Println("testExtStore failed.  want =", start, ", got =", got)
    75  		failed = true
    76  	}
    77  }
    78  
    79  var b int
    80  
    81  // testDeadStorePanic_ssa ensures that we don't optimize away stores
    82  // that could be read by after recover().  Modeled after fixedbugs/issue1304.
    83  //go:noinline
    84  func testDeadStorePanic_ssa(a int) (r int) {
    85  	defer func() {
    86  		recover()
    87  		r = a
    88  	}()
    89  	a = 2      // store
    90  	b := a - a // optimized to zero
    91  	c := 4
    92  	a = c / b // store, but panics
    93  	a = 3     // store
    94  	r = a
    95  	return
    96  }
    97  
    98  func testDeadStorePanic() {
    99  	if want, got := 2, testDeadStorePanic_ssa(1); want != got {
   100  		fmt.Println("testDeadStorePanic failed.  want =", want, ", got =", got)
   101  		failed = true
   102  	}
   103  }
   104  
   105  func main() {
   106  
   107  	testLoadStoreOrder()
   108  	testStoreSize()
   109  	testExtStore()
   110  	testDeadStorePanic()
   111  
   112  	if failed {
   113  		panic("failed")
   114  	}
   115  }