VMM/IEM: Implementation of f32_rsqrt (inverse square root) in Softfloat library, bugref:9898

git-svn-id: https://www.virtualbox.org/svn/vbox/trunk@98470 cfe28804-0f27-0410-a406-dd0f0b0b656f

2 files changed, 63 insertions, 0 deletions

diff --git a/src/libs/softfloat-3e/source/f32_sqrt.c b/src/libs/softfloat-3e/source/f32_sqrt.c
index ff5e169a0c6..e9bbfcceeec 100644
--- a/src/libs/softfloat-3e/source/f32_sqrt.c
+++ b/src/libs/softfloat-3e/source/f32_sqrt.c
@@ -119,3 +119,65 @@ float32_t f32_sqrt( float32_t a SOFTFLOAT_STATE_DECL_COMMA )
 
 }
 
+float32_t f32_rsqrt( float32_t a SOFTFLOAT_STATE_DECL_COMMA )
+{
+    union ui32_f32 uA;
+    uint_fast32_t uiA;
+    bool signA;
+    int_fast16_t expA;
+    uint_fast32_t sigA, uiZ;
+    struct exp16_sig32 normExpSig;
+    int_fast16_t expZ;
+    uint_fast32_t sigZ;
+    union ui32_f32 uZ;
+
+    /*------------------------------------------------------------------------
+    *------------------------------------------------------------------------*/
+    uA.f = a;
+    uiA = uA.ui;
+    signA = signF32UI( uiA );
+    expA  = expF32UI( uiA );
+    sigA  = fracF32UI( uiA );
+    /*------------------------------------------------------------------------
+    *------------------------------------------------------------------------*/
+    if ( expA == 0xFF ) {
+        if ( sigA ) {
+            uiZ = softfloat_propagateNaNF32UI( uiA, 0 SOFTFLOAT_STATE_ARG_COMMA );
+            goto uiZ;
+        }
+        if ( ! signA ) return a;
+        goto invalid;
+    }
+    /*------------------------------------------------------------------------
+    *------------------------------------------------------------------------*/
+    if ( signA ) {
+        if ( ! (expA | sigA) ) return a;
+        goto invalid;
+    }
+    /*------------------------------------------------------------------------
+    *------------------------------------------------------------------------*/
+    if ( ! expA ) {
+        if ( ! sigA ) return a;
+        normExpSig = softfloat_normSubnormalF32Sig( sigA );
+        expA = normExpSig.exp;
+        sigA = normExpSig.sig;
+    }
+    /*------------------------------------------------------------------------
+    *------------------------------------------------------------------------*/
+    expZ = 0x7F - ((expA - 0x7F)>>1) - 2;
+    expA &= 1;
+    sigA = (sigA | 0x00800000)<<8;
+    sigZ = softfloat_approxRecipSqrt32_1( expA, sigA );
+    sigZ >>= 1;
+
+    return softfloat_roundPackToF32( 0, expZ, sigZ SOFTFLOAT_STATE_ARG_COMMA);
+    /*------------------------------------------------------------------------
+    *------------------------------------------------------------------------*/
+ invalid:
+    softfloat_raiseFlags( softfloat_flag_invalid SOFTFLOAT_STATE_ARG_COMMA);
+    uiZ = defaultNaNF32UI;
+ uiZ:
+    uZ.ui = uiZ;
+    return uZ.f;
+
+}
diff --git a/src/libs/softfloat-3e/source/include/softfloat.h b/src/libs/softfloat-3e/source/include/softfloat.h
index 9df6177e235..e7c1637520a 100644
--- a/src/libs/softfloat-3e/source/include/softfloat.h
+++ b/src/libs/softfloat-3e/source/include/softfloat.h
@@ -223,6 +223,7 @@ float32_t f32_mulAdd( float32_t, float32_t, float32_t SOFTFLOAT_STATE_DECL_COMMA
 float32_t f32_div( float32_t, float32_t SOFTFLOAT_STATE_DECL_COMMA );
 float32_t f32_rem( float32_t, float32_t SOFTFLOAT_STATE_DECL_COMMA );
 float32_t f32_sqrt( float32_t SOFTFLOAT_STATE_DECL_COMMA );
+float32_t f32_rsqrt( float32_t SOFTFLOAT_STATE_DECL_COMMA );
 bool f32_eq( float32_t, float32_t SOFTFLOAT_STATE_DECL_COMMA );
 bool f32_le( float32_t, float32_t SOFTFLOAT_STATE_DECL_COMMA );
 bool f32_lt( float32_t, float32_t SOFTFLOAT_STATE_DECL_COMMA );